Systems and methods for controlling color temperature

ABSTRACT

Controlling the color temperature of a composite light source including at least one discrete-spectrum light source is disclosed. For example, the color temperature of a composite light source including at least one discrete-spectrum light source may be determined and/or adjusted based on one or more of the ambient color temperature of a space, the actual temperature of the space, the relative brightness of the space, the occupancy of the space, a time clock, a demand response command (e.g., from an electrical utility), the absolute location of the composite light source, the location of the composite light source relative to other light sources, inputs from a camera or other external devices, the operation of appliances or other machines in the vicinity of the composite light source, media content being utilized in the vicinity of the composite light source, and/or other sensor inputs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Non-Provisional patentapplication Ser. No. 16/534,921, filed on Aug. 7, 2019, which is acontinuation of U.S. Non-Provisional patent application Ser. No.15/996,569, filed Jun. 4, 2018, which is a continuation of U.S.Non-Provisional patent application Ser. No. 15/583,689, filed May 1,2017, now U.S. Pat. No. 9,992,841, issued Jun. 5, 2018, which is acontinuation of U.S. Non-Provisional patent application Ser. No.15/350,507, filed Nov. 14, 2016, now U.S. Pat. No. 9,668,315, issued May30, 2017, which is a continuation of U.S. Non-Provisional patentapplication Ser. No. 14/255,845, filed Apr. 17, 2014, now U.S. Pat. No.9,538,603, issued Jan. 3, 2017, which claims the benefit of U.S.Provisional Patent Application No. 61/814,109, filed Apr. 19, 2013, theentire disclosures of which are incorporated by reference herein intheir entireties.

BACKGROUND

Traditional sources of light such as the Sun (and later incandescentlights) may exhibit the characteristics of a black body radiator. Suchlight sources typically emit a relatively continuous-spectrum of light,and the continuous emissions range the entire bandwidth of the visiblelight spectrum (e.g., light with wavelengths between approximately 390nm and 700 nm). The human eye has grown accustomed to operating in thepresence of black body radiators and has evolved to be able todistinguish a large variety of colors when emissions from a black bodyradiator are reflected off of an object of interest.

Further, the frequency or wavelength of the continuous light spectrumemitted by a black body radiator may be dependent on the temperature ofthe black body radiator. Plank's law states that a black body radiatorin thermal equilibrium will emit a continuous-spectrum of light that isdependent on the equilibrium temperature of the black body. FIG. 1illustrates the Black Body Radiator Curve according to Plank's law.

As shown in FIG. 1, as the temperature of the black body radiatorincreases, the frequency of the peak of the emitted spectrum shifts tohigher frequencies. At room temperature (e.g., roughly 300 Kelvin (K)),the frequency peak is typically within the infrared portion of thespectrum and thus is imperceptible to the human eye. However, when thetemperature is increased to approximately 700-750 K, the blackbodyradiator will begin to emit light in the visible range of theelectromagnetic spectrum.

Typically, as the temperature of the black body radiator decreases, thewavelength of the emitted light increases and the frequency decreases,such that the emitted light appears “redder”. As the temperatureincreases, the peak of the emitted spectrum become “bluer” or decreasesin wavelength (e.g., increases in frequency). For black body radiators,this relationship between temperature and wavelength/frequency of theemitted light is inseparable—higher temperature radiators appear bluerand lower temperature radiators appear redder.

Thus, various wavelengths/frequencies of the visible light spectrum maybe associated with a given “color temperature” of a black body radiator.FIG. 2 illustrates an example comparison of the colors associated withdifferent color temperature values. The color temperature of a lightsource may refer to the temperature of an ideal black body radiator thatradiates light of comparable hue to that of the light source. As shownin FIG. 2, candlelight, tungsten light (e.g., from an incandescentbulb), early sunrise, and/or household light bulbs may appear to haverelatively low color temperatures, for example on the range of1,000-3,000 K. Noon daylight, direct sun (e.g., sunlight above theatmosphere), and/or electronic flash bulbs may appear to have colortemperature values on the order of 4,000-5,000 K and may have a greenishblue hue. An overcast day may appear to have a color temperature ofapproximately 7,000 K and may be even bluer than noon daylight. Northlight may be bluer still, appearing to have a color temperature on therange of 10,000 K.

Color temperatures over 5,000 K are often referred to as cool colors(e.g., bluish white to deep blue), while lower color temperatures (e.g.,2,700-3,000 K) are often referred to as warm colors (e.g., red throughyellowish white).

Incandescent and halogen lamps typically act as black body radiators.For example, a current is passed through a wire (e.g., a filament),causing the wire to increase in temperature. When the wire reaches acritical temperature, it begins to radiate light in the visiblespectrum. The color temperature of the radiated light is dictated byPlank's law. When an incandescent or halogen light is dimmed, thetemperature (and color temperature) is decreased, meaning that theemitter light becomes redder (e.g., higher wavelength, lower frequency).Thus, humans are accustomed to dimmed lights having a redder hue.

Recently, non-incandescent light sources such as fluorescent lights(e.g., compact fluorescent lights or CFLs) and light emitting diodes(LEDs) have become more widely available due to their relative powersavings as compared to traditional incandescent lamps. Typically lightfrom CFLs or LEDs does not exhibit the properties of a black bodyradiator. Instead, the emitted light is often more discrete in naturedue to the differing mechanisms by which CFLs and/or LEDs generate lightas compared to an incandescent or Halogen light bulbs. Sincefluorescents and LEDs do not emit relatively constant amounts of lightacross the visible light spectrum (e.g., instead having peakedintensities at one or more discrete points within the visible spectrum),fluorescents and LEDs are often referred to as discrete-spectrum lightsources.

The wavelength/frequency profile of a light source may be dependent onthe device or technique used to generate the light. For example, lightfrom fluorescent lamps is produced by electrically exciting mercurywithin a glass tube. The applied voltage causes the mercury to become aplasma that emits light in the ultraviolet (UV) frequency range.Typically, the glass tube is coated with a phosphorus-based materialthat absorbs the radiated UV light and then emits light in the visiblefrequency range. The wavelength shift from UV to the visible range isreferred to as Stokes shift. Depending on the properties of thephosphorus-based material, the wavelength/frequency of the light emittedmay be at different points within the visible spectrum. FIG. 3illustrates the discrete-spectrum emitted by an example CFL as comparedto an example continuous light source such as an incandescent lamp. Forexample, the line SP_(DISC-FLUOR) 310 may represent the relativeintensity of light emitted at various wavelengths by an example CFL, andthe line SP_(CONT) 320 may represent the relative intensity of lightemitted at the same wavelengths by an example incandescent lamp. As maybe seen in FIG. 3, the fluorescent light source may be characterized byone or more “bursts” of emissions at discrete frequencies/wavelengths.

Light from LEDs is produced due to the physical properties of asemiconducting material. For example, when a voltage is applied across asemiconductor junction that has different levels of electron dopingacross the boundary, an electric current is induced. When an electronfrom one side of the device recombines with an electron hole on theother, a photon is emitted. Depending on the semiconductor design, thephotons may be emitted at various wavelengths/frequencies within thevisible light spectrum. Like fluorescents, Stokes shift may cause thefrequency of the emitted photons to be lowered to achieve a desiredlight frequency output. FIG. 4 illustrates the discrete-spectrum emittedby an example LED as compared to an example continuous light source suchas an incandescent lamp. For example, the line SP_(DISC-LED) 410 mayrepresent the relative intensity of light emitted at various wavelengthsby an example LED, and the line SP_(CONT) 420 may represent the relativeintensity of light emitted at the same wavelengths by an exampleincandescent lamp. Like the emissions from the fluorescent lamp, the LEDlight may also be relatively discrete in nature.

When discrete-spectrum light sources are dimmed, their color temperaturemay not change in the same manner as black body radiators. For example,when incandescents and halogens are dimmed, their temperature isdecreased and the emitted light transitions to a lower color temperaturevalue (e.g., becomes redder) according to Plank's law. However, sincediscrete-spectrum light sources are not black body radiators, Plank'slaw may not apply. For example, both fluorescent lamps and LEDs maymaintain a relatively constant color temperature even in the presence ofdimming (e.g., and may actually become slightly bluer or higherfrequency as they are dimmed). Such an effect may be unnatural to thehuman eye, which may expect the color temperature to shift to a reddertemperature as the light dims. Moreover, when discrete-spectrum lightsources are placed in the vicinity of other light sources, for examplesources of light whose color temperature may change over time, thediscrete-spectrum light sources can appear unnatural or distracting.

SUMMARY

Methods and systems are disclosed for controlling the color temperatureof one or more light sources based on environmental criteria and/or userpreferences. For example, a composite lighting load including at leastone discrete-spectrum light source and at least one additional lightsource may be controlled by a load control system in order to vary thecolor temperature of the light emitted by the composite lighting load.For example, the color temperature of the at least one discrete-spectrumlight source may be determined and/or adjusted based on one or more ofthe ambient color temperature of a space, the actual temperature of thespace, the relative brightness of the space, the occupancy of the space,a time clock, a demand response command (e.g., from an electricalutility), the absolute location of the discrete-spectrum light source,the location of the discrete-spectrum light source relative to otherlight sources, inputs from a camera or other external devices, theoperation of appliances or other machines in the vicinity of thediscrete-spectrum light source, media content being utilized in thevicinity of the discrete-spectrum light source, and/or other sensorinputs. The light emitted from the composite lighting load may be maderedder (e.g., higher wavelength, lower frequency) in response to a firstset of criteria and/or the discrete-spectrum light source may be madebluer (e.g., lower wavelength, higher frequency) in response to a secondset of criteria.

For example, a system controller may be configured to control the colortemperature of one or more controllable-color-temperature lightingloads. Controllable-color-temperature lighting loads (CCTLLs) may alsobe referred to as color temperature controllable lighting loads. Thesystem controller may receive one or more input signals (e.g., ambientcolor temperature of a space, actual temperature of a space, therelative brightness of the space, the occupancy of the space, etc.) andmay send a signal indicating a determined color temperature and/or adetermined change in color temperature to the one or morecontrollable-color-temperature lighting loads. The indications may bespecific to each respective controllable-color-temperature lightingload. The controllable-color-temperature lighting loads may change theirrespective color temperature levels based on the signal received fromthe system controller.

In an example, the controllable-color-temperature lighting load mayinclude a control circuit and two or more discrete-spectrum lightsources. The discrete-spectrum light sources may be operably coupled toa color temperature load regulation system that is configured to varythe intensity of one or more of the discrete-spectrum light sources inorder to vary the color temperature of thecontrollable-color-temperature lighting load. For example, the colortemperature load regulation system may include load regulation circuitryconfigured such that the control circuit may vary the color temperatureof the combined emissions from the discrete-spectrum light sources. Thecontrol circuit may also be operably coupled to a communication circuitfor communicating with the system controller. In an example, rather thanor in addition to utilizing a system controller to control each of thecontrollable-color-temperature lighting loads in the system, thecontrollable-color-temperature lighting loads may be configured tocommunicate with each other and operate in an ad hoc manner.

BRIEF DESCRIPTION OF THE DRAWINGS

This patent or application file contains at least one drawing executedin color. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1 depicts an example of the black body color temperature curveaccording to Plank's law.

FIG. 2 illustrates an example comparison of the colors associated withdifferent color temperature values.

FIG. 3 depicts exemplary emissions of an example fluorescent lamp withinthe visible light spectrum.

FIG. 4 depicts exemplary emissions of an example LED within the visiblelight spectrum.

FIG. 5A depicts an example controllable-color-temperature lighting load.

FIG. 5B depicts an example controllable-color-temperature lighting loadthat utilizes two or more discrete-spectrum light sources.

FIG. 6 depicts an example a controllable-color-temperature lighting loadthat utilizes two or more LED lamps.

FIG. 7A depicts an example system where multiplecontrollable-color-temperature lighting loads may be in communicationwith a system controller.

FIG. 7B depicts an example system utilizing a plurality ofcontrollable-color-temperature lighting loads interacting in an ad hocmanner.

FIG. 7C depicts an example system that utilizes acontrollable-color-temperature lighting load including two LED lampsinstalled in a single lighting fixture.

FIG. 8 depicts a cross-section of an example room including one or moreCCTLLs.

FIG. 9 is a graph of example color temperature values for a plurality ofcontrollable-color-temperature lighting loads being matched to the colortemperature of an ambient light source.

FIG. 10 is a graph of example color temperature values for a pluralityof controllable-color-temperature lighting loads being utilized to forma color temperature gradient as the distance from an ambient lightsource increases.

FIG. 11 is another graph of example color temperature values for aplurality of controllable-color-temperature lighting loads beingutilized to form a color temperature gradient as the distance from anambient light source increases.

FIG. 12 is another graph of example color temperature values for aplurality of controllable-color-temperature lighting loads beingutilized to form a color temperature gradient as the distance from anambient light source increases.

FIG. 13 is another graph of example color temperature values for aplurality of controllable-color-temperature lighting loads beingutilized to form a color temperature gradient as the distance from anambient light source increases.

FIG. 14 is a flowchart depicting an example method for controlling oneor more controllable-color-temperature lighting loads.

FIG. 15 is a flowchart depicting an example method for adjusting theoverall intensity of a controllable-color-temperature lighting load.

DETAILED DESCRIPTION

The various systems and methods described herein may make reference todetermining, changing, or varying the color temperature of light source.For example, reference may be made to reddening a light source, making alight source redder, making a light source appear redder, shifting lighttowards red, warming the light, and/or otherwise shifting the light to ahigher wavelength/lower frequency. Such terms may refer to the processof changing the effective or composite color temperature of a lightsource to a lower color temperature. Similarly, the process of changingthe effective or composite color temperature of a light source to ahigher color temperature may be referred to as bluing a light source,making a light source bluer, making a light source appear bluer,shifting light towards blue, cooling the light, and/or otherwiseshifting the light to a lower wavelength/higher frequency. As may beappreciated, there may be numerous physical means for shifting the colortemperature of a discrete-spectrum light source.

For example, two or more discrete-spectrum light sources may becontrolled to vary the effective color temperature of a combined orcomposite light emitted from the two or more discrete-spectrum lightsources. When used herein, the term composite light or combined lightemitted from two or more light sources may refer to the mixed or jointemissions of light as seen from an observer at a distance away from thelight source. For example, the light sources may be included in a singlelight fixture, and to an observer in a room that includes the fixturethe composite light emitted by the two or more light sources may appearto be from as a single light source. The light fixture may or may notinclude a diffuser or other instrument that makes it appear thecomposite light emitted from the two or more discrete-spectrum lightsources is emitted from a single light source.

In another example, although a first light source may be included in adifferent lighting fixture than a second light source, the two lightsources may be located sufficiently close together from the perspectiveof an observer that their composite emissions appear to be from a singlelight source. As may be appreciated, the relative proximity of two ormore light sources that emit composite or combined light emissions mayvary depending on the position or distance of a desired target orobserver of the composite light emissions. For example, the two or morelight sources may be located relatively close together (e.g., in thesame fixture) if the target or observer of the composite light isrelatively close to the light sources (e.g., in the same room). However,if the target or observer is farther away, the two or more light sourcesmay be separated by a greater distance. Further, although an observerlooking directly at a CCTLL may be able to observe the two or moreindividual light sources, the CCTLL may be designed to provide a certaincolor temperature of light on a given surface. Thus, although theindividual light sources may be relatively far apart or may appear asdistinct light sources to a person staring at the CCTLL, the CCTLL maystill be configured to provide the desired color temperature of lightacross the target surface.

As noted above, the composite light may be the combined emissions of twoor more discrete-spectrum light sources. In another example, one or morediscrete-spectrum light sources may be used in combination with acontinuous-spectrum light source such as an incandescent or halogenlamp. The composite light emitted from such a device may include thelight emitted from the continuous-spectrum light source (e.g., andpotentially multiple continuous-spectrum light sources) and the one ormore discrete-spectrum light sources. Various combinations ofdiscrete-spectrum light sources and continuous-spectrum light sourcesmay be utilized, as is described in more detail herein.

As an example, as noted with respect to FIGS. 3 and 4, discrete-spectrumlight sources may be associated with various “spikes” or discreteportions of the electromagnetic spectrum at which the lamp radiatesrelatively intense emissions of light. The material used to coat theglass surrounding the discrete-spectrum light source (e.g., typically aphosphor or phosphor-like material) may cause the light to be emitted ata desired frequency range due to Stokes shift. For example, a firstdiscrete-spectrum light source may naturally emit light near the highfrequency end of the visible light spectrum (e.g., a LED may beconfigured to emit light with a color temperature on the range of 10,000K). A first coating may be applied to glass surrounding the firstdiscrete-spectrum light source in order to shift the light to a lowerfrequency (e.g., make the color temperature redder). Thus, the majorityof the light emitted from first discrete-spectrum light sourcesurrounded by the coated glass may be of a lower color temperature thanwould be emitted by the discrete-spectrum light source withoutencapsulating it in the glass.

Multiple discrete-spectrum light sources may be used to achieve variouseffective color temperatures. For example, if a first discrete-spectrumlight source has an effective color temperature in the red range (e.g.,on the order of 1,000 to 2,000 K) and a second discrete-spectrum lightsource has an effective color temperature in the blue range (e.g., onthe order of 10,000 K), then the total combined color temperature orcomposite color temperature of light emitted from the combination of thefirst discrete-spectrum light source and the second discrete-spectrumlight source may be of greenish hue (e.g., on the order of 4,000-5,000K) due to the human eye's perception of the composite light emitted bythe two light sources. As may be appreciated, by utilizing morediscrete-spectrum light sources emitting light associated with variouscolor temperature values, more exact color temperature control may beachieved.

For purposes of description, the term controllable-color-temperaturelighting load (CCTLL) may be used to refer to a device comprising atleast one discrete-spectrum light source, at least one additional lightsource, and one or more load control elements used to adjust theintensity of one or more of the at least one discrete-spectrum lightsource and the at least one additional light source in order to affectthe perceived color temperature of the combined or composite lightemissions from the at least one discrete-spectrum light source and theat least one additional light source. For example, a CCTLL may beimplemented using two or more discrete-spectrum light sources. The CCTLLmay include a load control system (e.g., having one or more load controlcircuits), and a composite lighting load having two or morediscrete-spectrum light sources that each emit light at different colortemperatures and that are each coupled to the load control system. Thecomposite lighting load emits a composite light output characterized bya composite color temperature. The load control system of the CCTLL maybe configured to control the intensity of at least one of the two ormore discrete-spectrum light sources in order to affect the compositecolor temperature of the emitted composite light output.

For example, the load control system may maintain a constant intensitylevel for a first discrete-spectrum light source and may vary theintensity of a second discrete-spectrum light source. Increasing theintensity of the second discrete-spectrum light source may cause thecomposite color temperature of the light sources to become closer tothat of the second discrete-spectrum light source. Decreasing theintensity of the second discrete-spectrum light source may cause thecomposite color temperature of the light sources to become closer tothat of the first discrete-spectrum light source. The load controlsystem of a CCTLL may be referred to as a controllable-color-temperatureload control system.

In another example, rather than maintaining a constant intensity levelat the first discrete-spectrum light source, the intensity levels ofboth the first discrete-spectrum light source and the seconddiscrete-spectrum light source may be varied in order to achieve adesired color temperature value for the composite emissions from thefirst and second discrete-spectrum light sources. For example, a systemcontroller and/or the load control system that controls the intensitylevels of the first and second discrete-spectrum light sources maymaintain a state table or other information in system memory thatassociates a desired color temperature value for composite lightemissions with intensity levels of the first and second light sources.Thus, the controlling device may be able to determine appropriateintensity levels for each of a plurality of discrete-light sources basedon the desired color temperature value of the composite light emitted bythe plurality of discrete-spectrum light sources.

Further, in addition to the desired color temperature value of thecomposite light being used to select appropriate intensity levels of thediscrete-spectrum light sources, the overall or combined intensity ofthe light may be used to select appropriate intensity levels for theunderlying discreet-spectrum light sources. For example in a CCTLL thatutilizes two-discrete spectrum light sources, a desired colortemperature value for the composite light emitted by the CCTLL may beachieved using various combinations of intensity levels of the first andsecond discrete-spectrum light sources. However, although differentcombinations of intensity levels for the first and seconddiscrete-spectrum light sources may be used to achieve approximately thesame color temperature value of the composite emissions, the differentcombinations may result in different overall intensity levels of thecomposite light (e.g., the overall composite intensity may be dimmer fora first combination and brighter for a second combination). Thus, thesystem controller and/or the load control system that controls theintensity levels of the first and second discrete-spectrum light sourcesmay determine the individual intensity levels of the first and seconddiscrete-spectrum light sources based on both the desired colortemperature value of the composite light and the desired overallintensity level of the composite light. Table 1 illustrates an examplestate table that may be maintained in order to determine appropriateintensity levels of the first and second discrete-spectrum light sourcesbased on a desired color temperature value of the composite light and adesired overall intensity level of the composite light.

TABLE 1 Desired Color Desired Intensity Level of Intensity Level ofTemperature Value of Intensity Level of First Discrete- Second Discrete-Composite Emissions (K) Composite Emissions Spectrum Light SourceSpectrum Light Source 8,000 L_(C1) L_(A1) L_(B1) 4,000 L_(C1) L_(A2)L_(B2) 2,000 L_(C1) L_(A3) L_(B3) 8,000 L_(C2) L_(A4) L_(B4) 4,000L_(C2) L_(A5) L_(B5) 2,000 L_(C2) L_(A1) L_(B6)

Thus, in the example shown in Table 1, if the desired color temperatureof emissions is approximately 8,000 K and the desired compositeintensity level is L_(C1), the first discrete-spectrum light source maybe set to intensity level L_(A1), and the second discrete-spectrum lightsource may be set to intensity level L_(B1). As an example, such acomposite color temperature and composite intensity level may correspondto the first discrete-spectrum light source operating at full intensity(e.g., L_(A1)=100%) and while the second-discrete spectrum light sourceoperates at half intensity (e.g., L_(B1)=50%). If the color temperatureis to be lowered to 4,000 K, but the overall composite intensity is toremain relatively constant, the first discrete-spectrum light source maybe set to intensity level L_(A2), and the second discrete-spectrum lightsource may be set to intensity level L_(B2). In some instances, such achange in color temperature may be achieved by varying the intensitylevel of a single discrete-spectrum light source of thediscrete-spectrum light sources. In another example, if the desiredcomposite color temperature is to remain constant at 8,000 K but theoverall composite intensity level is to be changed (e.g., dimmed) tolevel L_(C2), the first discrete-spectrum light source may be set tointensity level L_(A4), and the second discrete-spectrum light sourcemay be set to intensity level L_(B4). For example, such a compositeintensity level L_(C2) at color temperature 8,000 K may correspond tothe first discrete-spectrum light source operating at half intensity(e.g., L_(A4)=50%) and while the second-discrete spectrum light sourceoperates at quarter intensity (e.g., L_(B4)=25%).

Although the example described with respect to Table 1 utilizes twodiscrete-spectrum light sources, similar relationships may be determinedfor systems utilizing more than two discrete-spectrum light sources. Forexample, by utilizing more than two discrete-spectrum light sourceshigher degrees of granularity may be achieved for adjusting one or moreof the desired color temperature value of the composite emissions and/orthe desired intensity level of composite emissions. Additionally, inaddition to one or more discrete-spectrum light sources, one or morecontinuous-spectrum light sources may be used in a CCTLL. However, whendetermining appropriate intensity values for light source include in aCCTLL that includes at least one continuous-spectrum light source,Plank's law should be taken into account for the continuous-spectrumlight sources such that changes in intensity level may also change thecolor temperature of the light emitted by the continuous-spectrum lightsource. Such an effect may lead to non-linear relationships betweenintensity levels of light sources included in a CCTLL and the colortemperature of the combine emissions and/or or the composite intensitylevel of the emissions, for example.

The controllable-color-temperature load control system may bemanufactured and distributed separately from the light sources that itis configured to control. For example, thecontrollable-color-temperature load control system may be configured asan interface circuit that is installed in series with light sources thatmay be separately supplied.

FIG. 5A illustrates a block diagram of an examplecontrollable-color-temperature lighting load. For example, acontrollable-color-temperature lighting load 580 may include acontrollable-color-temperature load control system 550. Thecontrollable-color-temperature lighting load 580 may also include acomposite lighting load 570. The composite lighting load 570 may includea plurality of light sources. The controllable-color-temperature loadcontrol system 550 may be configured to control one or more of theindividual elements of the composite lighting load 570 in order toaffect the color temperature of the light emitted by the composite lightload.

For example, the composite lighting load 570 may include adiscrete-spectrum light source 556 and an additional light source 560.The additional light source 560 may be a discrete-spectrum light source,a continuous-spectrum light source, or a hybrid light source. Thecontrollable-color-temperature load control system 550 may be configuredto control the discrete-spectrum light source 556 and/or the additionallight source 560 in order to achieve a desired color temperature of thelight emitted by the composite lighting load 570.

In order to control the color temperature of the light emitted by thecomposite lighting load 570, the controllable-color-temperature loadcontrol system 550 may include a control circuit 552, a first loadregulation circuit 554, and a second load regulation circuit 558. Thecontrol circuit 552 may be configured to control the first control loadregulation circuit 554 in order to adjust the intensity ofdiscrete-spectrum light source 556. The control circuit 552 may beconfigured to control the second control load regulation circuit 558 inorder to adjust the intensity of additional light source 560. Thecontrol signals may be analog signals and/or digital signals.

In an example, the control circuit 552 may be configured to control thesecond load regulation circuit 558 such that the additional light source560 is maintained at a relatively constant intensity level. The controlcircuit 552 may then control the intensity of the discrete-spectrumlight source 556 in order to affect the overall color temperature of thelight emitted by the composite lighting load 570. In other examples, theintensity levels of both the discrete-spectrum light source 556 and theadditional light source 560 may be controlled in order to affect theoverall color temperature of the light emitted by the composite lightingload 570.

In an example, the controllable-color-temperature load control system550 may be included in a different device than the composite lightingload 570 (e.g., the controllable-color-temperature load control system550 may be located at a system controller, a dimmer, etc. and thecomposite lighting load 570 may be mounted at a lighting fixture), oreach of the controllable-color-temperature load control system 550 andthe composite lighting load 570 may be included in the same device(e.g., mounted in a lighting fixture). Further, thecontrollable-color-temperature load control system 550 may beimplemented in a single device or multiple devices. For example, thecontrol circuit 552 may be comprised of two (or more) individual controlcircuits for controlling the individual light sources of the compositelighting load 570. The individual control circuits may be in operativecommunication with each other and may be located in the same ordifferent devices. For example, the individual control circuits may eachbe configured to control an individual load regulation circuit (e.g.,one of the load regulation circuits 554, 558).

FIG. 5B illustrates an example controllable-color-temperature lightingload that is configured to vary the composite color temperature of lightemitted by two discrete-spectrum light sources. For example, acontrollable-color-temperature lighting load 530 may include acontrollable-color-temperature load control system 500. For example, thecontrollable-color-temperature load control system 500 may comprise adimmer switch, an electronic switch, an electronic ballast for one ormore gas discharge lamps (e.g., fluorescent lamps), an LED driver forLED light sources, etc. The controllable-color-temperature load controlsystem 500 may include a control circuit 502. The control circuit 502may include one or more general purpose processors, special purposeprocessors, conventional processors, digital signal processors (DSPs),microprocessors, microcontrollers, integrated circuits, a programmablelogic device (PLD), application specific integrated circuits (ASICs), orthe like. The control circuit 502 may perform signal coding, dataprocessing, power control, input/output processing, or any otherfunctionality that enables the load control device to perform asdescribed herein. An example of a load control device for an LED lightsource is described in commonly-assigned U.S. Patent ApplicationPublication No. 2011/0080110, published Apr. 7, 2011, entitled LOADCONTROL DEVICE FOR A LIGHT-EMITTING DIODE LIGHT SOURCE, the entiredisclosure of which is incorporated by reference herein.

For example, the control circuit 502 may send drive signals to a firstload regulation circuit (LRC) 504 to control the power provided to afirst discrete-spectrum light source 506. Although FIG. 5B may bedescribed in terms of discrete-spectrum light sources (e.g., LEDs,fluorescents, etc.), one or more non-discrete-spectrum light sources mayalso be utilized. For example, continuous-spectrum light source(s)and/or hybrid light source(s) may be utilized. An example of a hybridlight source is described in commonly-assigned U.S. Pat. No. 8,228,002,issued Jul. 24, 2012, entitled HYBRID LIGHT SOURCE, the entiredisclosure of which is incorporated by reference herein. The loadregulation circuit 504 may receive current via a hot line 518 and aneutral line 520 (e.g., from an alternating-current (AC) power source)and may provide an amount of power to discrete-spectrum light source506. The control circuit 502 may control the load regulation circuit 504in order to adjust the intensity of (e.g., dim) the discrete-spectrumlight source 506. For example, if the discrete-spectrum light source isan LED, the load regulation circuit 504 may include an LED driver thatcomprises a power converter circuit for generating a DC bus voltage anda LED drive circuit for receiving the bus voltage and adjusting themagnitude of the current conducted through the discrete-spectrum lightsource 506. The load regulation circuit 504 may be configured to adjustthe intensity of the discrete-spectrum light source 506, for exampleusing a pulse-width modulation technique or a constant current reductiontechnique. The load regulation circuit 504 may also include othercomponents for maintaining a desired quality of operation of thediscrete-spectrum light source 506. For example, the load regulationcircuit 504 may include a controllable-impedance circuit (e.g., a linearregulator).

A second load regulation circuit (LRC) 508 and a seconddiscrete-spectrum light source 510 may operate in a manner similar tothe first load regulation circuit 504 and the first discrete-spectrumlight source 506, although the second discrete-spectrum light source 510may be configured to emit a different color temperature of light thanthe first discrete-spectrum light source 506. One of thediscrete-spectrum light sources, such as the first discrete-spectrumlight source 506, may be configured to emit a relatively warm (e.g.,red) color temperature light, for example on the order of 1,000-2,000 K.The other discrete-spectrum light source, such as the seconddiscrete-spectrum light source 510, may be configured to emit arelatively cold (e.g., blue) color temperature light, for example on theorder of 10,000 K. Depending on the desired color temperature of thecombined/composite light source (e.g., the combination of the firstdiscrete-spectrum light source 506 and the second discrete-spectrumlight source 510), the intensities of one or more of the firstdiscrete-spectrum light source 506 or the second discrete-spectrum lightsource 510 may be adjusted (i.e., dimmed and/or increased).

As a result, the color temperature of the composite light emitted fromthe first discrete-spectrum light source 506 or the seconddiscrete-spectrum light source 510 may be controlled. For example, bydecreasing the intensity of the first discrete-spectrum light source 506and/or by increasing the intensity of the second discrete-spectrum lightsource 510, the composite light emitted may be made to appear to have ahigher color temperature than previously emitted (e.g., the lightappears bluer or cooler). Similarly, by decreasing the intensity of thesecond discrete-spectrum light source 510 and/or by increasing theintensity of the first discrete-spectrum light source 506, the compositelight emitted may be made to appear to have a lower color temperaturethan previously emitted (e.g., the light appears redder or warmer).

The first discrete-spectrum light source 506 and the seconddiscrete-spectrum light source 510 may be included in the same lightingfixture, for example so that the composite light emitted from thelighting fixture may be tuned to a desired color temperature. Thecontrollable-color-temperature lighting load may include a single powerconverter (e.g., rather than a power converter in each load regulationcircuit 504, 508) for generating a single DC bus voltage. The loadregulation circuits 504, 508 may each comprise an LED drive circuit forreceiving the DC bus voltage and controlling the respectivediscrete-spectrum light source 506, 510.

In an example, the discrete-spectrum light sources 506 may be integratedinto the same device (e.g., a screw-in lamp) or may be separate devices.For example, the discrete-spectrum light sources 506, 510 may beincluded in two fixtures that are in the vicinity of each other. In anexample, the load control system 500 may be a separate device that isattached to the discrete-spectrum light sources 506, 510. For example,the load control system 500 may be mounted to a lighting fixture andelectrically connected to the discrete-spectrum light sources 506, 510.In an example, load control system 500 and the discrete-spectrum lightsources 506, 510 may each be included in a single light fixture.Although two light sources may be illustrated in FIG. 5B, more than twolight sources may be utilized, for example to achieve more granularcontrol over color temperature and/or composite light intensity.

For example, if the control circuit 502 controls the first loadregulation circuit 504 to decrease the intensity of the firstdiscrete-spectrum light source 506 (e.g., the redder light source) whilemaintaining a constant intensity of the second discrete-spectrum lightsource 510, the combined light emitted from the first discrete-spectrumlight source 506 and the second discrete-spectrum light source 510 maybecome cooler in nature (e.g., more blue). Conversely, if the controlcircuit 502 controls the second load regulation circuit 508 to decreasethe intensity of the second discrete-spectrum light source 510 (e.g.,the bluer light source) while maintaining a constant intensity of thefirst discrete-spectrum light source 506, the combined light emittedfrom the first discrete-spectrum light source 506 and the seconddiscrete-spectrum light source 510 may be warmer in nature (e.g., morered). The control circuit 502 may be configured to control the firstload regulation circuit 504 and/or the second load regulation circuit508 in order to adjust the intensity of the first discrete-spectrumlight source 506 to a first intensity level (i.e., a first dimminglevel) and/or to adjust the intensity of the second discrete-spectrumlight source 510 to a second intensity level (i.e., a second dimminglevel) in order to achieve a desired color temperature and/or a desiredoverall intensity level of the composite light.

The control circuit 502 may be operably coupled to a communicationcircuit 512. The communications circuit 512 may include one or more of areceiver, a transmitter, a radio frequency (RF) transceiver, and/orother communications module(s) capable of performing wired and/orwireless communications via communications port 514. For example, thecontrol circuit 502 may be configured to communicate with othercontrollable-color-temperature lighting loads and/or a system controllervia the communications circuit 512. The communications may be analogand/or digital signals. The communications may include informationregarding the state information applicable to one or more of the controlcircuit 502, the first load regulation circuit 504, the firstdiscrete-spectrum light source 506, the second load regulation circuit508, and/or the second discrete-spectrum light source 510. Thecommunications may include information regarding the state of othercontrollable-color-temperature lighting loads and/or of the systemcontroller. The communications may include commands from one or more ofthe system controller and/or other controllable-color-temperaturelighting loads. The commands may instruct the control circuit 502 toadjust the intensities of one or more of the discrete-spectrum lightsources 506, 510, for example to achieve a desired composite colortemperature level. For example, the communications received by thecommunication circuit 512 may be an analog signal, for example rangingfrom 0-10 V (e.g., where 0 V may represent the lamp being turned off, 10V may represent full power, and linear interpolation may be used by thecontrol circuit 502 to determine power levels associated with theintervening range) and/or may be a digital control signal where discretepower levels/addresses are signaled to the load regulation circuit 504(e.g., to be used with a digital-to-analog (DAC) converter).

The control circuit 502 may store information in and/or retrieveinformation from a memory 516. For example, the memory 516 may storeinformation related to other controllable-color-temperature lightingloads and/or information communicated to/from a system controller. Thememory 516 may include a non-removable memory and/or a removable memory.The memory 516 may be non-transitory memory (e.g., tangible memory) thatis configured to store computer executable instructions to be performedand/or executed by the control circuit 502 in order to affect the colortemperature of the composite light emitted by the discrete-spectrumlight sources 506, 510. Although each of the communication circuit 512,the load regulation circuits 504, 508, and the memory 516 are shown tobe individually coupled to the control circuit 502, variousarchitectures may be utilized for exchanging information and otherwisecommunicating between the various components of thecontrollable-color-temperature load control system 500

In an example, once a specified color temperature has been achieved(e.g., a first intensity value has been determined for thediscrete-spectrum light source 506 and a second intensity value has beendetermined for the discrete-spectrum light source 510 such that thecombined emissions from the discrete-spectrum light source 506 and thediscrete-spectrum light source 510 are at the specified colortemperature), it may be desirable to dim the combined light output(e.g., decrease the total intensity of light emitted at the specifiedcolor temperature) without changing the specified color temperature. Toachieve the dimming without changing the color temperature, each of thediscrete-spectrum light source 506 and the discrete-spectrum lightsource 510 may be further dimmed while still maintaining a specifieddimming ratio between the discrete-spectrum light source 506 and thediscrete-spectrum light source 510. For example, suppose that a desiredcolor temperature may be achieved by dimming discrete-spectrum lightsource 506 to a 50% dimming level and by dimming discrete-spectrum lightsource 510 to a 25% dimming level. To decrease the overall intensity ofthe light emitted at the desired color temperature while still ensuringthe emitted light is at approximately the desired color temperature,discrete-spectrum light source 506 may be dimmed to a 25% dimming leveland discrete-spectrum light source 510 may be dimmed to a 12.5% dimminglevel. Thus, the ratio of the dimming level of discrete-spectrum lightsource 506 to the dimming level of discrete-spectrum light source 510may be maintained (e.g., 2 to 1) so that the emitted color temperaturemay remain approximately the same (e.g., albeit at a lower overallintensity).

In an example, the controllable-color-temperature lighting load 530 maybe configured to imitate the dimming properties of a continuous-spectrumlight source. For example, if the first discrete-spectrum light source506 is emitting light at a relatively warm color temperature and thesecond discrete-spectrum light source 510 is emitting light at arelatively cool color temperature, then to imitate the dimming effect ofa black body radiator the control circuit 502 may be configured to firstadjust the intensity of the second discrete-spectrum light source 510(e.g., the bluer light source) in order to vary the overall compositeintensity level of the controllable-color-temperature lighting load 530.In this manner, if the bluer discrete-spectrum is dimmed while theredder light source remains at a relatively constant intensity level,the overall composite intensity of the controllable-color-temperaturelighting load 530 may be decreased (e.g., dimmed) and the compositecolor temperature of the emitted light may become redder due to theincreased relative contribution of the redder light source to thecomposite light emissions. Similarly, if the bluer discrete-spectrum isbrightened while the redder light source remains at a relativelyconstant intensity level, the overall composite intensity of thecontrollable-color-temperature lighting load 530 may be increased (e.g.,brightened) and the composite color temperature of the emitted light maybecome bluer due to the increased relative contribution of the bluerlight source to the composite light emissions. Such effects may mimicthe natural dimming effects of a continuous-spectrum light source.

FIG. 6 illustrates an example a controllable-color-temperature lightingload for controlling using two or more LED light sources. Although twoLED light sources (e.g., a first LED light source 610 and a second LEDlight source 620) are shown in FIG. 6, more than two LED light sourcesmay be used. In an example, a controllable-color-temperature (CCT) loadcontrol device 600 may include a hot terminal 604 that is coupled to anAC power source 630. When used herein, the terms CCT load controldevice/circuit/system, color temperature load controldevice/circuit/system, load control device/circuit/system forcontrolling color temperature, load control device/circuit/system for aCCTLL, etc. may be used to describe one or more elements used to controlthe intensity level (e.g., dimming level) of one or more light sources(e.g., discrete-spectrum light sources) in order to vary the colortemperature of the composite light emitted by the one or more lightsources. For example, the CCT load control device 600 may include twodimmed hot terminals (e.g., a first dimmed hot terminal 606 and a seconddimmed hot terminal 616) for controlling the two LED light sources. Asmay be appreciated, there may be a dimmed hot terminal for each LEDlight source under the control of the CCT load control device 600.

The CCT load control device 600, the first LED light source 610, and thesecond LED light source 620 may be components of an example LED-drivenCCTLL. Various types of LEDs may be utilized. For example, LEDs thatemit light at different color temperatures may be used. In an example,one or more “tunable white” LEDs may be used. A tunable white LED mayemit light at a relatively white color temperature, but may also be“tuned” or adjusted to emit light at different color temperatures inaddition to the white light. For example, a tunable white LED may emitlight in a color temperature range from 2,700 K to 6,500 K, althoughother ranges may be used. The CCT load control device 600 may comprise acontrol circuit 602 for controlling a first dimmer circuit 605 togenerate a first dimmed hot voltage at the first dimmed hot terminal606. The CCT load control device 600 may comprise a second dimmercircuit 615 to generate a second dimmed hot voltage at the second dimmedhot terminal 616. The control circuit 602 may include one or moregeneral purpose processors, special purpose processors, conventionalprocessors, digital signal processors (DSPs), microprocessors,microcontrollers, integrated circuits, a programmable logic device(PLD), application specific integrated circuits (ASICs), or the like.The control circuit 602 may include memory (e.g., tangible memory) forstoring computer executable instructions to be performed by one or moreprocessors included in the control circuit 602.

For purposes of description, the example described with respect to FIG.6 may be explained using example analog control signals (e.g., usingphase control signals), but digital control signals may also be used.For example, rather than or in addition to providing the LED lightsources with an analog signal for controlling the LED light sources, theCCT load control device 600 may utilize digital signals to control theLED light sources 610, 620. The control circuit 602 may be operablycoupled to a communication circuit 608, which may provide operablecommunications between the CCT load control device 600, and one or moreof other controllable-color-temperature lighting loads, a systemcontroller, and/or various sensing equipment (e.g., an occupancy sensor,a daylight sensor, a color temperature sensor, and/or the like).

The dimmed hot terminal 606 may be coupled to a first load (e.g., thefirst LED light source 610), and the dimmed hot terminal 616 may becoupled to a second load (e.g., the second LED light source 620). Thefirst LED light source 610 may comprise an LED driver 612 and an LEDlight engine 614, and the second LED light source 620 may comprise anLED driver 622 and an LED light engine 624. The first LED light source610 may be coupled to the first dimmed hot terminal 606 and the neutralconnection of the AC power source 630. The second LED light source 620may be coupled to the second dimmed hot terminal 616 and the neutralconnection of the AC power source 630. The CCT load control device 600may be operable to provide a first dimmed hot voltage (e.g., a firstphase control signal) to the first LED light source 610 for controllingthe intensity of the LED light engine 614. The CCT load control device600 may be operable to provide a second dimmed hot voltage (e.g., asecond phase control signal) to the second LED light source 620 forcontrolling the intensity of the LED light engine 624. The first LEDlight source 610 may operate at a first color temperature (e.g., acooler color temperature, for example in excess of 10,000 K), and thesecond LED light source 620 may operate at a second color temperature(e.g., a warmer color temperature, for example in the approximate rangeof 1,000-3,000 K). By controlling the intensities of the first LED lightsource 610 and the second LED light source 620, the CCT load controldevice 600 may vary the combined output of the first LED light source610 and the second LED light source 620 to be a specified value betweenthe first color temperature and the second color temperature.

The CCT load control device 600 may be operable to provide the dimmedhot voltages using different types of phase control (e.g., forward phasecontrol, reverse phase control, etc.). In addition, the CCT load controldevice 600 may be operable to provide a full conduction voltage to oneor more of the LED light source 610 and/or LED light source 620. The CCTload control device 600 may include one or more control actuators (e.g.,tap switches) for turning the LED light engine 614 on and off, forturning LED light engine 624 on or off, and/or for turning both LEDlight engine 614 and LED light engine 624 on or off at the same time. Inan example, in addition to automatically controlling the intensitylevels of the LED light source 610 and the LED light source 620 based oncommands received from a system controller and/or inputs from varioussensing devices, the CCT load control device 600 may also include one ormore intensity adjustment actuators (e.g., dimming rockers). Theintensity adjustment actuators may be used to adjust the intensity ofthe first LED light engine 614, the second LED light engine 624, and/orboth of the first and second LED light engines 614, 624 at the sametime.

The LED driver 612 and/or the LED driver 622 may be configured toprovide power to various LED light engines. For example, the LED driver612 and the LED driver 622 may be operably coupled to analternating-current (AC) line voltage 626 used to supply power forilluminating the LED light engines 614, 624. The line voltage may besupplied by the CCT load control device 600 and/or may be separatelyconfigured connection with power source such as the AC power source 630.The different LED light engines may be rated to operate using differentload control techniques, different dimming techniques, and/or differentmagnitudes of load current and/or load voltage. The LED driver 612and/or the LED driver 622 may be operable (e.g., controllable via theCCT load control device 600) to control the load current through an LEDlight engine and/or the load voltage across an LED light engine.

In an example, the LED driver 612 and/or the LED driver 622 may beconfigured to utilize a current load control mode (e.g., control themagnitude of the current provided to the LED light engine) and/or avoltage load control mode (e.g., control the magnitude of the voltageprovided to the LED light engine). For example, in current load controlmode, the LED driver 612 and/or the LED driver 622 may control theintensity of the LED light engine (e.g., the LED light engine 614 and/orthe LED light engine 624, respectively) using a pulse-width modulationdimming technique and/or using a constant current reduction (CCR)dimming technique. When operating in voltage load control mode, the LEDdriver 612 and/or the LED driver 622 may control the intensity of theLED light engine (e.g., LED light engine 614 and/or LED light engine624, respectively) using a pulse-width modulation dimming technique.

The LED driver 612 and/or the LED driver 622 may each include aradio-frequency interference (RFI) filter and rectifier circuit forminimizing the noise inherent in the AC power source 630 and forgenerating a rectified voltage from the dimmed hot terminals. The LEDdriver 612 and/or the LED driver 622 may each include a power converter(e.g., a buck-boost flyback converter, a flyback converter, a buckconverter, a single-ended primary-inductor converter (SEPIC), a Ćukconverter, or other suitable power converter) to generate a variabledirect-current (DC) bus voltage. The power converter may provideisolation between the AC power source 630 and the LED loads (e.g., theLED light engine 614 and/or the LED light engine 624). The powerconverter may adjust the power factor of the LED driver to be close toone (e.g., appear as a near-entirely resistive load).

The LED driver 612 and/or the LED driver 622 may each include an LEDdrive circuit. The LED drive circuit may receive the bus voltage and maycontrol the amount of power delivered to the respective LED light engine(e.g., LED light engine 614 or LED light engine 624). The LED drivecircuit may include a controllable-impedance circuit (e.g., a linearregulator, a switching regulator, a buck converter, etc.) forcontrolling the intensity of the respective LED light engine. The LEDdriver 612 and/or the LED driver 622 may each include a control circuitfor controlling the operation of the power converter and/or the LEDdrive circuit. The control circuit may receive commands from the CCTload control device 600. In an example, the CCT load control device 600may directly control the power converters and/or LED drive circuitsincluded in the LED driver 612 and/or the LED driver 622. The LED driver612 and/or the LED driver 622 may each include a power supply forpowering the circuitry of LED drivers.

The LED driver 612 and/or the LED driver 622 may each include aphase-control input circuit for generating a target intensity controlsignal. The target intensity control signal may comprise, for example, asquare-wave signal with a duty cycle that is dependent upon theconduction period of a phase-control signal received from the CCT loadcontrol device 600. The target intensity signal may be representative ofthe target intensity of LED light engine being controlled. In anexample, the target intensity control signal may comprise a DC voltagehaving a magnitude dependent on the conduction period of thephase-control signal received from the CCT load control device 600, andmay be representative of the target intensity of LED light engine beingcontrolled. However, other types of control signaling may be utilized.

As an example, the LED light source 610 may be configured to operate ata relatively high color temperature, for example around 10,000 K (e.g.,a blue light source). The LED light source 620 may be configured tooperate at a relatively low color temperature, for example around2,000-3,000 K (e.g., a red light source). If it is determined that thecombined light source is to operate at a high color temperature, the CCTload control device 600 may increase the intensity of the LED lightsource 610 and/or decrease the intensity of the LED light source 620until the desired composite color temperature is achieved.

The CCT load control device 600 may be preconfigured with known dimmingvalue combinations for the LED light sources 610, 620 that will resultin various color temperatures. For example, the CCT load control devicemay include a state table that indicates a composite color temperaturethat will be emitted from the LED light sources 610, 620 based on thedimming/intensity levels utilized by the LED light sources 610, 620. Forexample, the CCT load control device may determine that a first colortemperature may be achieved when the first LED light source 610 isoperating at a first intensity level and the second LED light source 620is operating a second intensity level. By adjusting one or more of thefirst intensity level or the second intensity level, the resultant colortemperature may be adjusted. For example, increasing the secondintensity level at the second LED light source 620 may result in aredder or lower color temperature composite light.

The CCT load control device 600 may utilize feedback in order todetermine the current composite color temperature of the LED lightsources 610, 620. For example, a color temperature sensor may be used todetermine the color temperature of the composite light being emitted bythe LED light sources 610, 620 and may feedback the sensor informationto the CCT load control device. The CCT load control device 600 may usethe color temperature sensor data to adjust the intensity levels of oneor more of the LED light sources 610, 620 until a desired colortemperature is achieved.

FIG. 7A illustrates an example system where multiplecontrollable-color-temperature lighting loads may be in communicationwith a system controller. For example, a color temperature controllablelighting system 700 may include a system controller 702. The systemcontroller 702 may be configured to communicate with one or more of acontrollable-color-temperature lighting loads (CCTLLs) 704, 706, 708.Although three CCTLLs are shown in FIG. 7, more or fewer CCTLLs may beutilized. The communications may be wired and/or wireless communicationsand may be comprised of analog and/or digital signals. The systemcontroller 702 may send commands to one or more of the CCTLLs 704, 706,708 that indicate the appropriate color temperature that the respectiveCCTLL should operate at (or otherwise control the respective CCTLL inorder to cause it to operate at the desired color temperature). Forexample, the command may indicate an amount by which the CCTLL shoulddim one or more light sources included in the CCTLL. The command mayindicate a desired color temperature for a respective CCTLL, and theCCTLL may determine the appropriate adjustment to the intensity of agiven light source in order to achieve the desired color temperature.

The system controller 702 may act as a control node for the CCTLLs in anarea and/or for other controllable equipment in a given area. Forexample, the system controller 702 may receive various sensor dataand/or feedback information from the CCTLLs. The system controller 702may be configured to determine the appropriate color temperature for theCCTLLs and/or the appropriate settings for other controllable equipmentin the area (e.g., shades, non-CCTLL lighting equipment, temperaturesettings, control of climate control equipment such as air conditionersand heaters, control of security equipment, control of appliances orelectronics in an area, etc.). The system controller 702 may include auser interface for receiving user preferences or for establishingdefault settings. The system controller 702 may determine theappropriate color temperature for one or more CCTLLs based onenvironmental criteria (e.g., sensor readings, current time, inputs frommedia/media devices, etc.) and/or user settings or preferences (e.g., adesired color temperature level, a desired room temperature level, theindicated use of the room, etc.). The system controller 702 may inferbased on settings and/or sensor readings when and how to automatically(e.g., without direct input from a user) change the color temperature ofone or more CCTLLs in a given area.

As an example, the system controller 702 may determine to operate theCCTLL 704 at 2,000 K, the CCTLL 706 at 4,000 K, and the CCTLL 708 at7,000 K. The system controller 702 may send a digital message to theCCTLL 704 indicating that the CCTLL 704 should operate at 2,000 K. In anexample, the system controller 702 may send a command to the CCTLL 704that indicates the amount by which the CCTLL 704 should adjust theintensities of one or more light sources included in CCTLL 704. Forexample, the command may be similar to a phase-control signal sent froma dimmer switch. In another example, the command may be a digitalcommand. The system controller 702 may send similar commands to theCCTLL 706 and the CCTLL 708 in order to instruct them to operate at4,000 K and 7,000 K, respectively.

The CCTLLs 704, 706, 708 may each include a communication circuitconfigured to communicate with other CCTLLs and/or the system controller702. The CCTLLs 704, 706, 708 may each also include two or more lightsources. The two or more light sources may be discrete-spectrum lightsources (e.g., LED light engines) that are associated with two or moredifferent color temperatures. The two or more light sources may includea continuous-spectrum light source such as an incandescent lamp or ahalogen lamp. The CCTLLs 704, 706, 708 may each also include a CCT loadregulation system such as two or more load regulation circuits tocontrol the respective light sources. The CCT load regulation systems ofCCTLLs 704, 706, 708 may each also include a control circuit configuredto interpret commands received from the system controller 702 and/orother CCTLLs and to implement the commands by controlling the intensityof the two or more light sources, for example using the two or more loadregulation circuits.

The system controller 702 may also be in communication with a daylightsensor 710, an occupancy sensor 712, and/or a color temperature sensor714. Although the daylight sensor 710, the occupancy sensor 712, and thecolor temperature sensor 714 are shown in FIG. 7, other types of sensorsmay also be utilized. For example, the system controller 702 may beoperably coupled to one or more of a motion sensor, a vacancy sensor, atime clock, a calendar, a weather sensor, a location sensing device(e.g., Global Positioning System (GPS)), a media device (e.g., computer,smartphone, tablet, television, music player, camera), a shadow sensor,a light intensity sensor, a temperature sensory, a smoke detector, aCarbon Dioxide (CO₂) sensor, and/or the like. The system controller 702may be configured to interpret the information received from one or moresensors (e.g., such as the daylight sensor 710, the occupancy sensor712, the color temperature sensor 714, and/or any other sensors) todetermine an appropriate color temperature for the CCTLLs 704, 706, 708.In addition, the controller 702 may also be in communication with amanual input device, such as, a keypad or remote control device having auser interface (e.g., including one or more actuators) for receiving auser input.

For example, the occupancy sensor 712 may be configured to provide anindication to the system controller 702 when one or more persons arepresent in a given room or space. A characteristic of discrete-spectrumlight sources may be that they operate more efficiently (e.g., producemore lumens per watt) when operating at a higher color temperature(e.g., bluer) than at a lower color temperature (e.g., redder). The moreefficient operation may be due to fewer losses during the Stokes shiftto a lower frequency. However, bluer light may also be lessaesthetically pleasing to the human eye. Therefore, during periodswherein the occupancy sensor 712 indicates that the room or space (inwhich the CCTLL 704, the CCTLL 706, and/or the CCTLL 708 is installed)is occupied, the system controller 702 may be configured to control theCCTLL 704, the CCTLL 706, and/or the CCTLL 708 such that thecorresponding light sources operate at a redder color temperature (e.g.,in order to operate in an aesthetically pleasing manner). During periodswhen the occupancy sensor 712 indicates that the room or space is notoccupied, the system controller 702 may be configured to control theCCTLL 704, the CCTLL 706, and/or the CCTLL 708 to operate the lightsources using a bluer temperature (e.g., in order to operate moreefficiently).

In an example, the daylight sensor 710 may be configured to provide anindication to the system controller 702 regarding the approximate amountof ambient light that is detected by the daylight sensor 710. Thedaylight sensor 710 may provide an indication of the total intensity oflight detected, an indication of the relative intensity of light in agiven bandwidth (e.g., the visible light spectrum), and/or the like. Thesystem controller 702 may receive the information regarding the amountof ambient light from the daylight sensor 710 and may adjust the lightsources of one or more of the CCTLLs 704, 706, 708 based on theinformation. For example, the system controller 702 may control each ofthe CCTLLs 704, 706, 708 to adjust the total intensity of light emittedfrom each CCTLL without changing the specified color temperature of eachCCTLL (e.g., by maintaining a specified dimming ratio between the lightsources of each CCTLL) in response to the daylight sensor 710. Forexample, the daylight sensor 710 may be used to feedback overall lightintensity information to the system control 702 such that the systemcontroller 702 adjusts the overall intensity of the light emitted fromthe CCTLLs 704, 706, 708 while maintaining relatively constant colortemperatures and/or a ratio of color temperatures across the CCTLLs 704,706, 708.

In an example, since daylight may be associated with a relatively highcolor temperature (e.g., on the order of 5,000-10,000 K), during periodswhere daylight is detected by the daylight sensor 710, the systemcontroller 702 may be configured to instruct one or more of the CCTLLs704, 706, 708 to operate at a relatively high color temperature. Bymatching the output from one or more of the CCTLLs 704, 706, 708 to thatof daylight, a more aesthetically pleasing appearance may be achieved.During periods were little or no daylight is detected, the systemcontroller 702 may be configured to instruct one or more of the CCTLLs704, 706, 708 to operate using a relatively low color temperature (e.g.,redder). Such a lower color temperature may be more aestheticallypleasing to the human eye in the absence of other light sources such asdaylight.

In an example, the color temperature sensor 714 may be configured tomeasure the color temperature of the ambient light received by the colortemperature sensor and to provide an indication to the system controller702 regarding the relative intensity of light at a given colortemperature. The color temperature sensor 714 may indicate thedetermined color temperature of the ambient light to the systemcontroller 702 in order for the system controller 702 to determine thecolor temperature of operation for one or more of the CCTLLs 704, 706,708. For example, the system controller 702 may attempt to match thecolor temperature of one or more of the CCTLLs 704, 706, 708 with thecolor temperature of the ambient light detected by the color temperaturesensor 714. In an example, the color temperature sensor 714 (or anothercolor temperature sensor) may be used to measure the color temperatureof light emitted by one or more of the CCTLLs 704, 706, 708, for exampleto provide feedback regarding the operation of the CCTLLs 704, 706, 708to the system controller 702.

As an example of operation of the color temperature controllablelighting system 700, if it is an overcast day, the color temperaturesensor 714 may detect a color temperature of approximately 7,000 K forambient light. The system controller 702 may use this information toinstruct one or more of the CCTLLs 704, 706, 708 to adjust theintensities of one or more of their respective light sources in order toachieve a color temperature of approximately 7,000 K to be emitted fromthe CCTLL 704, the CCTLL 706, and/or the CCTLL 708. By matching thecolor temperature to that of the ambient light outside the building, notonly can a more aesthetically pleasing environment be created inside thebuilding, but also the building may blend in more with the surroundingsand may attract less attention from persons on the outside of thebuilding when the color temperature inside the building matches that ofthe light outside. Thus, a benefit of additional privacy can be achievedsince what is happening inside the building may not stand out as much toan observer outside the building.

Moreover, due to the differing effects that warm versus cool colortemperatures can have on humans, the color temperature of lights withina space or room may be varied in order to achieve a desired effect. Forexample, studies have shown that cognitive tasks such as reading maybenefit from utilizing relatively cooler, bluer light. Thus, forclassroom or work settings, it may be desirable to achieve a relativelyhigh color temperature for the overall room. Thus, in addition to anyavailable daylight, the CCTLLs within a classroom or work setting may beset to a relatively high color temperature. However, for more creativeworks such a painting or other artistry, some studies have shown that awarmer, redder light source is more beneficial. Thus, for studios orother creative settings, the CCTLLs may be set to a relatively low colortemperature.

The system controller 702 may also be in communication with one or moredaylight control devices, for example, a motorized window treatment 716.The motorized window treatment (MWT) 716 may be positioned in front of awindow for controlling the amount of daylight (e.g., natural light)entering the building. The motorized window treatment 716 may be openedto allow more daylight to enter the building and may be closed to allowless daylight to enter the building. The motorized window treatment 716may comprise one or more of a roller shade, a drapery, a roman shade, acellular shade, a venetian blind, and/or a skylight shade. Examples ofmotorized window treatments are described in commonly-assigned U.S. Pat.No. 6,983,783, issued Jan. 10, 2006, entitled MOTORIZED SHADE CONTROLSYSTEM, and/or U.S. Patent Application Publication No. 2012/0261078,published Oct. 18, 2012, entitled MOTORIZED WINDOW TREATMENT, the entiredisclosures of which are hereby incorporated by reference. In anexample, the system controller 702 may be in communication with othertypes of daylight control devices, such as, for example, one or more ofcontrollable window glazings (e.g., electrochromic windows),controllable exterior shades, and/or controllable shutters or louvers.

FIG. 7B illustrates an example where one or more CCTLLs may operate in arelatively autonomous or ad hoc manner (e.g., without the use of adedicated system controller). For example, CCTLLs 752, 754, 756, 758 maybe co-located in a room or common space. The CCTLLs 752, 754, 756, 758may be configured to communicate with each other, or the CCTLLs 752,754, 756, 758 may be configured to operate wholly autonomously (e.g.,without communicating with other CCTLLs and/or without interactionbetween the different CCTLLs when setting the operational colortemperatures).

One or more of the CCTLLs 752, 754, 756, 758 may be operably coupled toone or more sensors. For example, CCTLL 752 may be coupled to andreceive input data from a daylight sensor 760, an occupancy sensor 762,and/or a color temperature sensor 764. Although not shown in FIG. 7B,one or more of the CCTLLs 754, 756, 758 may be configured to utilize thesame sensors as the CCTLL 752 and/or may be configured to use its ownsensors. The CCTLLs 752, 754, 756, 758 may communicate with a motorizedwindow treatment (MWT) 766 in order to adjust the operation of themotorized window treatment 766 and/or to take into account the currentstate of the motorized window treatment 766 when determining theappropriate CCTLL color temperature state.

The CCTLL 752 may use the information received from one or more sensors(e.g., the daylight sensor 760, the occupancy sensor 762, the colortemperature sensor 764, and/or the like) to adjust its color temperaturesetting. For example, the CCTLL may be configured to match the colortemperature of ambient light as detected by the color temperature sensor764. If the color temperature sensor 764 indicates that the colortemperature of the ambient light has increased (e.g., become bluer), theCCTLL 752 may respond by increasing the intensity of a relatively bluelight source and/or by decreasing the intensity of a relatively redlight source. The amount by which the CCTLL 752 increases the intensityof a relatively blue light source and/or decrease the intensity of arelatively red light source may depend on one or more of the amount ofchange in color temperature to be achieved, the nominal colortemperature of the bluer light source, the nominal color temperature ofthe redder light source, the relative proximity of the desired colortemperature relative the nominal color temperature of the bluer lightsource/redder light source, and/or the like.

FIG. 7C illustrates an example system that utilizes a dual-LED drivenCCTLL. For example, a system 770 may include a CCTLL 774. The CCTLL 774may include two or more LED drivers 775 configured to power two or moreLED light engines 776. As an example, the CCTLL 774 may be implementedusing similar components as were described in FIG. 6. The load controlsystem for the CCTLL 774 may be included at the CCTLL 774 and/or may beincluded at a system controller 772. The system controller 772 mayadjust the composite color temperature of the CCTLL 774 based on inputsreceived from a daylight sensor 780, a color temperature sensor 784, anoccupancy sensor 782, another CCTLL (e.g., a CCTLL 778), a motorizedwindow treatment (MWT) 786, other sensors, and/or the like. Controlsignals for adjusting a particular, individual LED may be individuallysent to the CCTLL 774 (e.g., the system controller 772 sends individualdigital or analog commands for adjusting a specific LED intensity)and/or the a single command may be sent that causes the CCTLL 774 toadjust the intensity of multiple LEDs (e.g., the System Controller 772indicates a given color temperature value to the CCTLL 774 and the CCTLL774 determines how to individually adjust each of the LEDs based on thecommand).

In an example, each of the CCTLLs within a given room may all be set toapproximately the same color temperature. For example, the colortemperature may be set to that of the ambient daylight (e.g., asmeasured by a color temperature sensor/daylight sensor located near awindow) and/or some other color temperature. For example, FIG. 8 mayrepresent a cross-section of an example room including one or moreCCTLLs. For example, a room 800 may include one or more window(s) 802,which may be located on one side of the room. Although the room 800 isshown to have the window(s) 802 on a single wall in FIG. 8, other wallsmay also include windows.

Additionally, one or more rows of CCTLLs may be included on the ceilingof the room 800. As may be appreciated, although three rows of CCTLLsare shown in FIG. 8, more or fewer rows may be utilized. Additionally,although examples may be described in terms of controlling rows ofCCTLLs together, respective CCTLLs within a given CCTLL row may becontrolled individually. For example, if additional windows are includedon a wall perpendicular to the wall containing the window 802, it may bedesirable to individually control CCTLLs included in a given CCTLL rowin order to achieve a desired effect (e.g., maintaining a desired levelof color temperature within room 800). Further, rather than or inaddition to rows of CCTLLs, various geometric arrangements of CCTLLs maybe used to outfit a room. The manner used to control the colortemperature operation of the CCTLL arrangements may depend of thegeometric arrangement utilized and the desired color temperature effect(e.g., match a desired color temperature, introduce a color temperaturegradient, etc.).

As shown in FIG. 8, a CCTLL row 804, a CCTLL row 806, and a CCTLL row808 may be located on the ceiling of the room 800. Although the CCTLLsare shown to be on the ceiling in FIG. 8, CCTLL rows and/or individualCCTLLs may be included in various configurations throughout room 800.CCTLL row 804 may be located closest to the window 802, followed by theCCTLL row 806, and the CCTLL row 808 may be the furthest CCTLL row awayfrom the window 802. A motorized window treatment (e.g., a motorizedroller shade 812) may be mounted adjacent the window 802 to control theamount of daylight entering the room 800, or the effect that daylighthas on the color temperature in the room.

Depending on the desired lighting effect within room 800, a systemcontroller (e.g., not shown in FIG. 8) may be configured to control thecolor temperature emitted by the light sources of one or more of theCCTLL rows 804, 806, 808. The system controller may automatically (e.g.,inferred by the device itself based on sensor readings and/orpre-programmed settings) change the color temperature of one or more ofthe CCTLL rows 804, 806, 808. The system controller may also beconfigured to control automated blinds or shades that are configured topartially and/or completely block light from entering the room 800 viathe window 802.

In an example, the system controller may receive an indication of thecolor temperature of the ambient light received through the window 802.The system controller may then send an indication to each of the CCTLLrows 804, 806, 808 to match the color temperature of the ambient lightentering through the window 802. FIG. 9 is a graph illustrating anexample where the color temperature of each of the CCTLL rows is matchedto the ambient color temperature entering the room via the window 802.For example, a color temperature sensor may measure the colortemperature of the window light to be approximately 5,000 K (e.g., noondaylight). The sensor reading may be sent to a system controller, whichmay instruct each of the CCTLL rows 804, 806, 808 to emit light at 5,000K. Each of the CCTLL rows 804, 806, 808 may then control the intensityof one or more light sources to achieve a color temperature output ofapproximately 5,000 K. By matching the color temperature of each lightsource in the room to the ambient light from the window 802, a moredesirable aesthetic effect may be achieved and the contents of the roommay be less visible from the outside.

In an example, rather than setting the color temperature of each of theCCTLL rows to the ambient daylight color temperature, a gradient may beapplied to the color temperature emitted by the CCTLL rows. For example,the CCTLL row closest to the window 802 (e.g., the CCTLL row 804) may beset to the color temperature of the ambient light entering the room 800via the window 802. The next closest CCTLL row to the window 802 (e.g.,the CCTLL row 806) may be set to a color temperature level above orbelow that of the ambient light entering via the window 802. Forexample, for some scenarios it may provide a desirable aesthetic effectto impart a color temperature gradient wherein the color temperaturebecomes gradually warmer (e.g., redder) as you move further from thewindow 802. Therefore, the CCTLL row 806 may be set to a lower colortemperature than the CCTLL row 808. Similarly, the CCTLL row 804 may beset to a lower color temperature than the CCTLL row 806.

FIG. 10 illustrates an example where a gradient may be applied to theCCTLL rows in order to gradually warm the light as you move further fromthe ambient light source (e.g., a window). As shown in FIG. 10, theambient light entering through the window 802 may be approximately 7,000K (e.g., an overcast day). The color temperature of the CCTLL row 808may be set to match that of the ambient light entering via the window802 (e.g., 7,000 K). The next CCTLL row (e.g., the CCTLL row 806) may beset to a warmer color temperature than that of the CCTLL row 808. Forexample, the CCTLL row 806 may be set to a color temperature ofapproximately 5,000 K, although other values may be utilized. Similarly,the CCTLL row 804 may be set to a warmer color temperature than that ofthe CCTLL row 806. For example, the CCTLL row 804 may be set to a colortemperature of approximately 3,000 K, although other values may beutilized.

In another example, rather than making the color temperature warmer asthe CCTLL rows move further from the window, the CCTLL rows may beconfigured to become increasingly cool (e.g., bluer) in value, forexample to achieve a desired aesthetic effect. FIG. 11 illustrates anexample where a gradient may be applied to the CCTLL rows in order togradually cool the light as you move further from the ambient lightsource (e.g., a window). As shown in FIG. 11, the ambient light enteringthrough the window 802 may be approximately 2,000 K (e.g., earlysunrise). The color temperature of the CCTLL row 808 may be set to matchthat of the ambient light entering via the window 802 (e.g., 2,000 K).The next CCTLL row (e.g., the CCTLL row 806) may be set to a coolercolor temperature than that of the CCTLL row 808. For example, the CCTLLrow 806 may be set to a color temperature of approximately 3,000 K,although other values may be utilized. Similarly, the CCTLL row 804 maybe set to a cooler temperature than that of the CCTLL row 806. Forexample, the CCTLL row 804 may be set to a color temperature ofapproximately 4,000 K, although other values may be utilized.

In an example, rather than setting the color temperature of each of theCCTLL rows to the ambient daylight color temperature, it may bedesirable for the overall (e.g., composite) light within a room to be arelatively constant color temperature irrespective from its distancefrom an ambient light source. For example, suppose it is an overcastday, and that the ambient light entering the room 800 via the window 802is approximately 7,000 K. However, it may be desirable that the lightwithin the room 800 have a color temperature of approximately 5,000 K.Since the intensity of light from the window 802 is lessened as you movefurther from the window 802 and closer to the door 810, a gradient maybe applied to the color temperature emitted by the CCTLL rows in orderto achieve a relatively constant color temperature of approximately5,000 K throughout the room. Thus, the CCTLL row closest to the window802 (e.g., the CCTLL row 808) may be set to a relatively low colortemperature in order to counter the effects of the relatively high colortemperature ambient light entering via the window 802. Since the ambientlight from the window 802 may be less intense at the CCTLL row 806 thanat the CCTLL row 808, the CCTLL row 806 may be set to a slightly highercolor temperature than the CCTLL row 808, since a less warm colortemperature may be used to counteract the effects of ambient light fromthe window 802 at the location of the CCTLL row 806. Similarly, an evencooler color temperature may be used at the CCTLL row 804 since theambient light from the window 802 may be even less intense at thelocation of the CCTLL row 804 than it is at the CCTLL row 806.

FIG. 12 illustrates an example where a gradient may be applied to theCCTLL rows in order to achieve a relatively constant color temperatureacross a space that is different than the color temperature of anambient light source in the space (e.g., ambient light entering via awindow). As an example, the room may be a restaurant, and it may be moredesirable to have the room lit with a relatively warmer (e.g., redder)light in order to achieve a desired lighting effect. In this example,suppose that the ambient daylight entering the room 800 via the window802 has a color temperature of approximately 7,000 K (e.g., an overcastday) and the desired color temperature within the room 800 isapproximately 5,000 K. The color temperature of the CCTLL row 808 may beset to the lowest (e.g., warmest) value of the CCTLL rows since theeffects of the ambient light from the window 802 (e.g., at 7,000 K) maybe strongest at the closest CCTLL row.

For example, the CCTLL row 808 may be set to a value in the range of2,000 K. The next CCTLL row (e.g., the CCTLL row 806) may be set to acooler color temperature than that of the CCTLL row 808, but the colortemperature of the CCTLL row 806 may still be set to a value lower thanthe desired 5,000 K since the ambient light from the window 802 maystill affect the overall light color temperature at the location of theCCTLL row 806. For example, the CCTLL row 806 may be set to a colortemperature value in the range of 3,000 K. The final CCTLL row (e.g.,the CCTLL row 804) may be set to a cooler color temperature than that ofthe CCTLL row 806, but the color temperature of the CCTLL row 804 maystill be set to a value lower than the desired 5,000 K since the ambientlight from the window 802 may still affect the overall light colortemperature at the location of the CCTLL row 804. For example, the CCTLLRow 804 may be set to a color temperature value in the range of 4,000 K.It may be noted that the values selected for this example are exemplaryin nature, and the actual values utilized may be selected based onfactors such as the geometry of the room, the amount of ambient lightentering the room via the window, the color temperature of other CCTLLsand/or other light sources within the room, the rate at which theambient light grows less intense as you move further from the window,etc.

In an example, CCTLL rows in a given area may be set to achieve agradient of color temperatures within a room. For example, rather thanattempting to have the overall color temperature in the room be a givencolor temperature, the color temperature of the CCTLL rows may be set togrow increasingly warm or increasing cool as you move closer to or awayfrom a given side of the room. FIG. 13 illustrates an example where thecolor temperature of the CCTLLs may be set to be gradually warmer as youmove further from a window. As shown in FIG. 13, the ambient lightentering via the window 802 may have a color temperature ofapproximately 7,000 K. Each of the CCTLL rows may have their respectivecolor temperatures set to be increasing warmer than the ambient lightentering through the window. For example, the CCTLL row 808 may have acolor temperature that is lower than the light entering from the window802. The CCTLL row 806 may be set to have a lower color temperature thanthat of the CCTLL row 808. The CCTLL row 804 may be set to have a lowercolor temperature than that of the CCTLL row 806. In this manner, agradient may be achieved such the overall color temperature of lightreflecting off objects near the window may be cooler than the colortemperature of the light reflecting off of objects near the door 810.

In an example, in addition to controlling the CCTLLs within a givenvicinity, a system controller may also be configured to control one ormore automated window shades in the vicinity. For example, some humansmay have a physiological response to warmer (e.g., redder) light thatmakes them feel as if an ambient temperature in the room (or space) iswarmer than it actually is. Such an effect may be utilized inconjunction with CCTLLs to potentially save energy used for heating abuilding. For example, suppose it is a cold, overcast day during thewinter. The color temperature of the ambient light entering a room onsuch a day may be in the range of 7,000 K and the temperature may be inthe range of 30° F. Typically, the heating and/or cooling system for theroom may be set to near 70° F. on such a day. However, a systemcontroller may be in communication with a color temperature sensorand/or a room temperature sensor (e.g., a thermometer or thermostat). Inorder to make it appear that the room is warmer than it actually is, thesystem controller may send a command to automated window shades thatindicates that the shades should partially or fully obscure therelatively cool (e.g., 7,000 K) light entering via a window.Additionally, the system controller may instruct one or more CCTLLswithin the room to operate using a relatively warm color temperature,for example in the range of 1,000-3,000 K. By changing the overall colortemperature of the room to be warmer, the thermostat may be set to alower temperature than it typically would given the weather conditions,for example in the range of 65° F. The light with a relatively red colortemperature may have the effect of making a person in the room feel asif the 65° F. room with redder light is just as warm as the 70° F. roomwith bluer light. In this way, large amounts of energy savings may beachieved due to the energy intensive nature associated with heating theroom the extra 5° F.

In an example, a CCTLL may be utilized to “match” the color temperatureof other light sources in an area. For example, a room may include oneor more continuous-spectrum light sources that operate at a givenbrightness level. If one of the continuous-spectrum light sources fails,it may be desirable to replace the failed continuous-spectrum lightsource with discrete-spectrum light sources, for example to achieveenergy savings. However, it may be difficult to match the colortemperature of the continuous-spectrum light sources with that of adiscrete-spectrum light source, and without matching the colortemperatures of the light sources, the replacement discrete-spectrumlight source may look unnatural or out-of-place. Thus, a CCTLL may beutilized instead of the traditional discrete-spectrum light source. Forexample, a CCTLL with a color temperature sensor may be installed withthe continuous-spectrum light sources. The color temperature sensor mayindicate the approximate color temperature of the continuous-spectrumlight sources to the CCTLL. The CCTLL may then adjust its colortemperature to match that of the continuous-spectrum light sources inorder to provide an aesthetically pleasing appearance.

In another example, a CCTLL may be utilized to match the colortemperature of other discrete-spectrum light sources in an area. Forexample, over time discrete-spectrum light sources may degrade orotherwise change their color temperature profile. Thus, even though agiven discrete-spectrum light source was designed to have a given colortemperature, over time the discrete-spectrum light source may beginemitting light at a different color temperature. Therefore, it may bedifficult to find another discrete-spectrum light source that matchesthe color temperature of the degraded discrete-spectrum light source. Inan example, a CCTLL may be used to match the color temperature of thedegraded discrete-spectrum light source. A CCTLL with a colortemperature sensor may be installed with the degraded discrete-spectrumlight source(s). The color temperature sensor may indicate theapproximate color temperature of the degraded discrete-spectrum lightsource(s) to the CCTLL. The CCTLL may then adjust its color temperatureto match that of the degraded discrete-spectrum light source(s) in orderto provide an aesthetically pleasing appearance.

A system controller and/or one or more CCTLLs may utilize feedback fromone or more sensors. For example, the sensors may provide informationregarding the current state of the CCTLLs. As noted above,discrete-spectrum light sources may have their color temperature changeor degrade over time. Since a CCTLL may be comprised of two or morediscrete-spectrum light sources, CCTLL operation may be effected bychanges in the characteristics of one or more of its underlyingdiscrete-spectrum light sources. For example, the control circuit and/orthe system controller for a CCTLL may expect that each of thediscrete-spectrum light sources included in a CCTLL emits light at agiven color temperature. The system controller and/or control circuitmay rely on this expectation to determine the appropriate dimming valuesfor the discrete-spectrum light sources included in the CCTLL. Thus, ifone or more of the discrete-spectrum light sources included in the CCTLLdegrade or otherwise change their color temperature response, the CCTLLmay emit light with a composite color temperature different than what isconfigured/expected by the system controller and/or control circuit.

Therefore, a sensor such as a color temperature sensor may be utilizedto provide feedback to the system controller and/or control circuitregarding the current state of one or more CCTLLs. For example, a colortemperature sensor may be designed to measure the color temperatureemitted by one or more discrete-spectrum light sources included in aCCTLL, the composite color temperature of light emitted by a givenCCTLL, and/or the composite color temperature of light emitted by aplurality of CCTLLs. The system controller and/or control circuit mayutilize the feedback information to correct for degradation of one ormore discrete-spectrum light sources and/or to otherwise adjust theoperation of the CCTLLs.

As an example, a color temperature sensor may be configured to measurethe color temperature of composite light emitted by the two or morediscrete-spectrum light sources included in a CCTLL. The colortemperature sensor may provide the measurements as feedback to thecontrol circuit of the CCTLL and/or a system controller. The controlcircuit may adjust the intensity level of one or more of thediscrete-spectrum light sources based on the feedback. For example, ifthe feedback indicates that color temperature of the emitted light islower (e.g., warmers, redder) than what was expected, the controlcircuit may increase the intensity level of a warmer discrete-spectrumlight source of the CCTLL and/or may decrease the intensity level of acooler discrete-spectrum light source of the CCTLL. In an example,rather than or in addition to monitoring the color temperature of thecomposite light emitted from the CCTLL, a color temperature sensor maymeasure the color temperature emitted by one or more of thediscrete-spectrum light sources included in a CCTLL. The informationregarding the color temperature emitted by one or more of thediscrete-spectrum light sources included in a CCTLL may be fed back to asystem controller and/or to the control circuit of the CCTLL. The systemcontroller and/or the control circuit of the CCTLL may utilize thefeedback information when determining the amount by which each of thetwo or more discrete-spectrum light sources should be dimmed in order toachieve a desired color temperature output from the CCTLL.

In an example, the color temperature of one or more CCTLLs in a spacemay be set based on a current use of the space or an activity occurringin the space. For example, if a room is being used for a businessmeeting, a system controller may determine to set the CCTLLs in the roomto a relatively cooler color temperature to encourage/facilitateproductivity. The system controller may receive an indication of thecurrent use of the room via a user interface or the like (e.g., a sceneor preset selection), and/or may infer the current use of the room basedon sensor readings or other inputs. The user interface may be includedat the system controller. In an example, if the room is included in anoffice building, the system controller (e.g., and/or a control circuitof the CCTLL) may utilize a time clock, an occupancy sensor, and/orother sensors to determine the color temperature to be used for one ormore CCTLLs in the room. For instance, during business hours, the CCTLLsmay be set to a cooler color temperature in order to encourageproductivity. However, after business hours, the CCTLLs may be set towarmer temperatures (e.g., if an occupancy sensor indicates the room isoccupied after normal business hours) so that the room may be moreamenable to a more social, relaxed setting.

Gradients of color temperature within a room may be set based on adetermined or inferred use of the room. For example, an engineer'soffice may include a desk with a computer workstation on one side of theroom and a work bench on the other side of the room. It may be desirableto set the CCTLLs near the desk to a first color temperature and theCCTLLs near the work bench to a second color temperature. For example,the CCTLLs near the desk may be set to a cooler color temperature andthe CCTLLs near the work bench may be set to a warmer color temperature.In an example, the CCTLLs within the engineer's office may be set to thesame color temperature and the color temperature that is set may dependon the position of a person within the office. For example, if anoccupancy sensor detects a person near the desk, the CCTLLs in the roommay be set to a cooler color temperature. If the occupancy sensordetects that the person moves to or is otherwise near the workbench, thecolor temperature of the CCTLLs may be changed to a warmer colortemperature.

In an example, a system controller and/or a control circuit of a CCTLLmay infer a use of the room, for example based on sensor readings, andmay set an appropriate color temperature of one or more CCTLLs based onthe inferred use. For example, if an occupancy sensor indicates that aroom is occupied, but a motion sensor indicates that the person(s) arenot moving (e.g., the occupants are relatively stationary), the systemcontroller and/or a control circuit of a CCTLL may infer that theoccupant is reading or otherwise working. In this scenario, the systemcontroller and/or the control circuit of the CCTLL may set one or moreCCTLLs to a cooler color temperature to facilitate productivity orencourage productive reading. Rather than or in addition to using theoccupancy sensor/motion detector, a camera may be used to determine thelocation of persons within a room and/or to infer the current use of aroom. For example, picture or video analysis techniques may be utilizedto determine the number of people in a room, the relative amount ofmovement in the room, and/or other information about the use of the roomsuch that the system controller and/or the control circuit of the CCTLLmay determine an appropriate color temperature setting for one or moreCCTLLs in the room. For example, if it is determined that a room has acertain number of occupants (e.g., more than three, although othervalues may be utilized), the system controller and/or the controlcircuit of a CCTLL may determine that the room is being used for socialpurposes and may set one or more CCTLLs to a relatively warm colortemperature setting.

In an example, the system controller and/or the control circuit of aCCTLL may determine to gradually change the color temperature of one ormore CCTLLs over time. For example, a room may originally be set to usea relatively warm color temperature. However, since discrete-spectrumlight sources may operate more efficiently (e.g., produce more lumensper watt) at a cooler color temperature, the system controller and/orthe control circuit of a CCTLL may determine to gradually cool one ormore CCTLLs in the room in order to save energy. By transitioning moregradually, people within the room may be unaffected since the change isnot abrupt (e.g., the persons may not notice the gradual change in colortemperature). In an example, the CCTLLs may default to turning on to arelatively warm color temperature and may autonomously, graduallytransition (e.g., based on control information received from a systemcontroller and/or control circuit) to a cooler color temperature thelonger they are left on.

In an example, lighting for an emergency exit (and/or other areas suchas stairwells, hallways, or rooms) may be set to a relatively cool colortemperature setting when unoccupied (e.g., such that the CCTLLs operatemore efficiently), but may be transitioned to a warmer color temperaturewhen occupied. In an example, the CCTLLs used for emergency lighting maybe powered by electricity from the electric grid or from an emergencyback-up source (such as an emergency generator or battery backup forwhen grid electricity is unavailable). During periods where the CCTLLsare powered by regular electrical grid sources the CCTLLs may be set tofirst color temperature (e.g., a warmer color temperature) and duringperiods where the CCTLLs are powered by the emergency backup source, theCCTLLs may be set to a second color temperature (e.g., a cooler, morepower efficient color temperature).

In an example, an electric utility or other entity may indicate periodsof higher energy use to a system controller and/or control circuit of aCCTLL. For example, the indication may include a demand response commandthat indicates that an electric grid is under a relatively high load.For example, during the daytime during the summer, the electric grid maybe running near capacity. The electric utility may indicate that costsavings may be achieved if a given user reduces their energy use duringthe periods. In response to such demand response commands, the systemcontroller and/or the control circuit of the CCTLL may control one ormore CCTLLs to transition to a cooler color temperature in order to saveenergy. In an example, the determination to transition to a cooler (orwarmer) color temperature may be based on the current price ofelectricity on the grid. Other examples indicating periods during whicha CCTLL may operate using a bluer color temperature in order to operatein a power savings mode are described in commonly-assigned U.S. Pat. No.8,417,388, issued Apr. 9, 2013, entitled LOAD CONTROL SYSTEM HAVING ANENERGY SAVINGS MODE, the entire disclosure of which is incorporated byreference. Similarly, certain buildings may operate in an “afterhours”mode, where equipment is powered at more power efficient settings whenin afterhours mode. In an example, when in afterhours mode, CCTLLs mayoperate using bluer light than is used during normal (e.g., business)hours.

In an example, a system controller and/or a control circuit of a CCTLLmay determine an appropriate color temperature for one or more CCTLLsbased on the current time of day and/or the current time of the year.For example, during periods near the beginning and end of the daytime(e.g., sunrise and sunset, respectively) the color temperature of one ormore CCTLLs may be set to a relatively warm color temperature to mimicthe color temperature from the sun, and during the middle of the day thecolor temperature may be set to a cooler color temperature. In anexample, during the winter months, the color temperature may be set to awarmer color temperature in order to encourage people to “feel” warmereven though it may be cold outside. Conversely, during the summermonths, the color temperature may be set to a cooler temperature sinceit may be hotter outside.

In an example, the color temperature may be set based on the orientationof a building. For example, rooms on a building's north side (e.g.,which in the Northern Hemisphere may receive less direct sunlight) maybe set to a first color temperature and rooms on the building's southside may be set to a second color temperature. A shadow sensor may alsobe used to determine the appropriate color temperature. In an example,the color temperature may be set based on the location (e.g., latitudeand longitude) of the CCTLL. For example, CCTLLs in more tropicalregions may be set to a first color temperature and CCTLLs in moretemperate regions may be set to a second color temperature.

In an example, the appropriate color temperature may be set based onmedia being utilized in a given area. For example, if a projector is inuse, the system controller and/or control circuit may infer the room isbeing utilized for a presentation. The color temperature of CCTLLs inthe room may then be set to a relatively warm color temperature tocontrast with the projector screen. In an example, the color temperaturemay be set based on one or more applications being executed on acomputing device. For example, if presentation application is beingexecuted on the computing device and/or the presentation application isbeing displayed on the display of the computing device, the systemcontroller and/or control circuit may determine that the colortemperature in the room should be set to a warmer color temperature. Ifa word processing application is running or active, the systemcontroller and/or control circuit may determine that the colortemperature in the room should be set to a cooler color temperature.

In an example, the system controller and/or control circuit maydetermine the appropriate color temperature based on the type content ofmedia being utilized in the vicinity. For example, a first colortemperature be utilized if a first media device is in operation (e.g., atelevision) and a second color temperature may be utilized if a secondmedia device is in operation (e.g., a video game console). In anexample, the color temperature may be set based on the identity of themedia content being utilized. For example, for a horror movie the systemcontroller and/or control circuit may determine that the colortemperature in the room should be set to a first color temperature(e.g., a cooler color temperature), but for a romantic movie the systemcontroller and/or control circuit may determine that the colortemperature in the room should be set to a second color temperature(e.g., a warmer color temperature).

In an example, the system controller and/or control circuit maydetermine that the color temperature in the room should be set to agiven color temperature based on the appliances in operation in thevicinity. For example, if a television is turned on, the systemcontroller and/or control circuit may determine that the colortemperature in the room should be set to a warmer color temperature. Inan example, if the system controller and/or control circuit determinesthat certain devices are not in operation, the system controller and/orcontrol circuit may infer the room is not occupied and may set the colortemperature to a cooler color temperature to conserve energy.

In an example, the system controller and/or control circuit maydetermine that the color temperature in the room should be set to agiven color temperature based on weather conditions. For example, duringperiods of snow, the CCTLLs may be set to a first color temperature(e.g., a warmer color temperature so that people may feel warmer) andduring hot, sunny days the CCTLLs may be set to a second colortemperature (e.g., a cooler color temperature so that people feelcooler). As an example, the system controller and/or control circuit mayhave internet access to obtain the weather information or otherinformation utilized to make decisions regarding the appropriate colortemperature of a CCTLL.

In an example, multiple CCTLLs may be used to guide people within anarea. For example, during emergency scenarios the CCTLLs within a roomor hallway may indicate a path to an emergency exit. For example, a lineor path of CCTLLs operating at a relatively cool color temperature maybe used to indicate the path to the emergency exit. Other CCTLLs not onthe path to the emergency exit may be set to a warmer color temperature(e.g., as well as dimmed). In an example, a gradient of colortemperatures may be used to guide people to an emergency exit. Forexample, the CCTLLs closest to the emergency exit may be set to a verycool color temperature and CCTLLs furthest from the emergency exit maybe set to a very warm color temperature. The remaining CCTLLs may behave their color temperature set based on a gradient, where the colortemperatures become increasingly cool as distance from the emergencyexit decreases.

In an example, the CCTLLs may be used as a commissioning tool foridentifying the addresses of the CCTLLs. Examples of commissioning toolsand/or lighting load commissioning methods are described incommonly-assigned U.S. patent application Ser. No. 13/796,877, filedMar. 12, 2013, entitled IDENTIFICATION OF LOAD CONTROL DEVICES, and/orU.S. patent application Ser. No. 13/830,237, filed Mar. 14, 2013,entitled, COMISSIONING LOAD CONTROL SYSTEMS, the entire disclosures ofwhich are incorporated by reference herein. In an example, wheninstalling and configuring lighting systems, an installer/administratormay attempt to identify which lighting loads and/or CCTLLs areassociated with a given zone or identifier in the lighting controlsystem. In an example, in order to differentiate CCTLLs in differentzones and/or different addresses, during a commissioning mode the CCTLLsmay be set to a determined color temperature depending on which zone oraddress the CCTLL is associated with. For example, CCTLLs associatedwith a first zone or address may be set to a first color temperature,CCTLLs associated with a second zone or address may be set to a secondcolor temperature, etc. In an example, a camera (such as a cameraincluded in a smart phone) may be used to take a picture or video of theCCTLLs during commissioning. An analysis of the picture/video may thenbe performed to determine which CCTLLs are associated with whichaddress/zone.

FIG. 14 is a flowchart depicting an example method for controlling thecolor temperature of the light emitted by one or more CCTLLs. Forexample, the method depicted by FIG. 14 may be implemented by a systemcontroller. Similar methods may be implemented by a control circuit of aCCTLL.

For example, at 1402, sensor data from one or more sensors may bereceived. The sensor data may include one or more of occupancy data,ambient light data (e.g., color temperature data, light intensity data,light frequency data, etc.), data regarding appliances in use, datarelated to the power source for the CCTLL, position data, temperaturedata, time data, date data, data from the Internet, weather data, dataregarding media being utilized, etc. Information regarding userpreferences or settings may also be received or determined.

At 1404, appropriate color temperature values for one or more CCTLLs maybe determined. The determination of the appropriate color temperaturevalue may be based on one or more of the sensor data, informationrelated to the layout of the room/space including the CCTLLs,information regarding the relative location of the CCTLL(s) with respectto each other, information regarding the relative location of theCCTLL(s) with respect to ambient light sources, information regardingthe layout of the space/room that includes the CCTLLs, user preferencesor settings, an inferred use of the space/room including the CCTLLs,etc.

At 1406, command(s) indicating the appropriate color temperaturesetting/value may be sent to the one or more CCTLLs. The one or moreCCTLLs may be set to the same or different color temperature values. TheCCTLLs may transition to the appropriate color temperature(s) based onthe command. The command may be a digital or analog signal that may besent wirelessly or via wired communication lines. For example, if acommand indicates that a given CCTLL is to operate at a relativelyhigher (e.g., bluer) overall color temperature, the CCTLL may beconfigured to increase the intensity of a relatively high colortemperature discrete-spectrum light source and/or to lower the intensityof a relatively low color temperature discrete-spectrum light source.Conversely, if a command indicates that a given CCTLL is to operate at arelatively lower (e.g., redder) overall color temperature, the CCTLL maybe configured to increase the intensity of a relatively low colortemperature discrete-spectrum light source and/or to lower the intensityof a relatively high color temperature discrete-spectrum light source.

At 1408, new sensor data and/or feedback information from one or more ofthe CCTLLs may be received. For example, an occupancy sensor mayindicate that all people have left the room. The feedback informationmay include, for example, information from sensors included at the oneor more CCTLLs, information related to the state of one or more of theCCTLLs, and/or other information that may be useful in identifying anappropriate color temperature value for the one or more CCTLLs. A newcolor temperature value may be determined for one or more CCTLLs basedon the updated data. At 1410, a command may be sent to one or more ofthe CCTLLs that instructs the one or more CCTLLs to operate at anupdated color temperature value.

FIG. 15 is a flowchart depicting an example method for adjusting theoverall intensity of the light emitted by a CCTLL without significantlyaffecting the color temperature of the composite light. The methoddepicted by FIG. 15 may be implemented by a system controller. Similarmethods may be implemented by a control circuit of a CCTLL, for exampleif the CCTLL is operating autonomously.

For example, at 1502, the CCTLL may be set to a desired colortemperature value and a desired intensity level. For example, the CCTLLmay be originally set at a maximum achievable intensity level for a givecolor temperature value upon initiating operation. For example, this maybe the case when the CCTLL is initially turned or powered on. However,various combinations of intensity level and color temperature may be setat 1502. For example, the intensity level and/or color temperature maybe set based on sensor data from one or more sensors. As noted above,the sensor data may include one or more of occupancy data, ambient lightdata (e.g., color temperature data, light intensity data, lightfrequency data, etc.), data regarding appliances in use, data related tothe power source for the CCTLL, position data, temperature data, timedata, date data, data from the Internet, weather data, data regardingmedia being utilized, etc. Information regarding user preferences orsettings may also be received or determined in order to determine theappropriate overall intensity level and/or color temperature value touse for the CCTLL based on the received sensor data. When referring toFIG. 15, the intensity level of the CCTLL may refer to the intensity ofthe composite or combined light emitted by a plurality of light sourcescomprised in the CCTLL.

At 1504, a target intensity level (or an adjustment amount by which theoverall intensity level may be adjusted) may be determined. In theexample of FIG. 15, the overall intensity level may be adjusted withoutsubstantially affecting the color temperature of the light emitted fromthe CCTLL (e.g., the overall intensity level is adjusted withoutsubstantially changing the color temperature of the emitted light). Forexample, the system controller may determine to dim the CCTLL to thetarget intensity level, for instance upon receiving a user inputrequesting that the light be dimmed to the target intensity level. Basedon the target intensity level, at 1506 the system controller may sendone or more commands to the CCTLL to adjust the intensity of the CCTLLto the target intensity level. For example, the system controller maysend individual commands indicating the individual intensity levels oflight sources in the CCTLL (or the amounts by which the individualintensity levels of light sources in the CCTLL should be adjusted). Inan example, the system controller may send a command indicating theamount by which the total light intensity of the CCTLL should beadjusted, and the CCTLL may independently determine the change inindividual light source intensities that would result in the commandedtotal intensity change while maintaining a relatively constant colortemperature.

Irrespective of whether the system controller and/or the CCTLLdetermines the individual intensity level changes of the light sourcesin the CCTLL, the total intensity level of the CCTLL may be adjusted bymaintaining a desired intensity ratio between the individual lightsource elements of the CCTLL while decreasing (e.g., to dim) orincreasing (e.g., to brighten) each of the individual light sourceelements. For example, if a given CCTLL is comprised of threediscrete-spectrum light sources, and a desired color temperature isachieved by operating a first discrete-spectrum light source at a firstintensity level, a second discrete-spectrum light source at a secondintensity level, and a third discrete-spectrum light source at a thirdintensity level, then in order to dim the overall combined intensitylevel of the CCTLL by about a third, the first intensity level may belowered by a third, the second intensity level may be lowered by athird, and third intensity level may be lowered by a third. Conversely,to increase the overall combined intensity level of the CCTLL by about athird, the first intensity level may be increased by a third, the secondintensity level may be increase by a third, and third intensity levelmay be increased by a third. Although three light sources per CCTLL areused for this example, more or fewer light sources may be used in aCCTLL and the overall intensity level may be increased or decreased byadjusting the component intensity levels while maintaining a specifiedratio between the component light source intensity levels.

Although the example of dimming (or brightening) the CCTLL by a third isdescribed as individually adjusting the intensity of the light sourcesby a third, in some scenarios the individual light source adjustmentsmay be different than the overall intensity adjustment. For example,depending on the respective color temperature values of light emitted bythe individual light sources of a given CCTLL, it may be that a givencolor temperature value and overall composite intensity level may beachieved using various combinations of intensities at the individuallight sources. For example, a decrease in overall intensity of a CCTLLby a third may be achieved by dimming each of the individual lightsources by a third or by powering off one of the light sourcescompletely while varying the intensity levels of the two other lightsources in order to obtain the desired composite color temperature andintensity level. Utilizing a greater number of light sources in a CCTLLmay increase the number of potential combinations of individualintensity levels for light sources that result in the same compositecolor temperature and the same composite light intensity.

At 1508, new sensor data, user commands, and/or feedback informationfrom one or more of the CCTLLs may be received. For example, anoccupancy sensor may indicate that all people have left the room, andthe device may be programmed to dim the CCTLLs while maintaining aconstant color temperature of the composite light emissions. In anexample, a user may select a new dimming value (i.e., the targetintensity level) using an input device such as a dimmer. The feedbackinformation may include, for example, information from sensors includedat the one or more CCTLLs, information related to the state of one ormore of the CCTLLs, and/or other information that may be useful inidentifying an appropriate color temperature value for the one or moreCCTLLs. Based on the updated data, the system controller may send anupdated command to the CCTLL to adjust the overall intensity level whilemaintaining a constant color temperature.

At 1510, the system controller may send an updated command to the CCTLL,for example based on the updated inputs determined at 1508. For example,if the sensor data at 1508 indicated that the room is no longeroccupied, the system controller may send a command to decrease theoverall intensity level of emitted light by half. The CCTLL may then dimthe individual light sources—for example while maintaining the samerelative intensity ratio between the light sources—in order to achievethe desired intensity change (e.g., dimming the CCTLL by 50% whilemaintaining a constant color temperature).

What is claimed:
 1. A lighting color temperature control method,comprising: receiving, by control circuitry, an output signal from oneor more sensors in a space; determining, by the control circuitry, atarget color temperature for the space based on the received outputsignal; determining, by the control circuitry, a ratio of a first outputlevel of light having a first color temperature to a second output levelof light having a second color temperature different from the firstcolor temperature to achieve the target color temperature;communicating, by communications interface circuitry communicativelycoupled to the control circuitry, a first control output that includesdata indicative of the determined first output level, the first controloutput to cause a first lighting load to provide illumination at thefirst color temperature at the first output level; and communicating, bythe communications interface circuitry, a second control output thatincludes data indicative of the determined second output level, thesecond control output to cause a second lighting load to provideillumination at the second color temperature at the second output level.2. The method of claim 1 wherein communicating the first control outputto the first lighting load and communicating the second control outputto the second lighting load comprises: communicating, by thecommunications interface circuitry, the first control signal and thesecond control signal to a single lighting fixture that includes boththe first lighting load and the second lighting load.
 3. The method ofclaim 2 wherein receiving the output signal from the one or more sensorsin the space further comprises: receiving, by control circuitry disposedremote from the first lighting load and the second lighting load, theoutput signal from the one or more sensors in the space.
 4. The methodof claim 1 wherein communicating the first control output to the firstlighting load and communicating the second control output to the secondlighting load comprises: communicating, by the communications interfacecircuitry, the first control output to a first lighting fixture thatincludes the first lighting load; and communicating, via thecommunications interface circuitry, the second control output to asecond lighting fixture that includes the second lighting load, thesecond lighting fixture remote from the first lighting fixture.
 5. Themethod of claim 4 wherein receiving the output signal from the one ormore sensors in a space further comprises: receiving, by controlcircuitry disposed in either the first lighting load or the secondlighting load, the output signal from the one or more sensors in thespace.
 6. The method of claim 4 wherein receiving the output signal fromthe one or more sensors in a space further comprises: receiving, bycontrol circuitry disposed in both the first lighting load and thesecond lighting load, the output signal from the one or more sensors inthe space.
 7. The method of claim 1 wherein receiving the output signalfrom the one or more sensors in a space further comprises: receiving, bythe control circuitry, an output signal that includes informationindicative of a measured color temperature of daylight present in thespace, the output signal provided by one or more daylight sensors. 8.The method of claim 7 wherein determining the target color temperaturefor the space based on the received output signal further comprises:matching, by the control circuitry, the target color temperature to themeasured color temperature of the daylight present in the space.
 9. Themethod of claim 1 wherein receiving the output signal from the one ormore sensors in a space further comprises: receiving, by the controlcircuitry, an output signal that includes information indicative of anoccupant present in the space, the output signal provided by one or moreoccupancy sensors.
 10. The method of claim 9 wherein determining thetarget color temperature for the space based on the received outputsignal further comprises: selecting, by the control circuitry, a firsttarget color temperature for the space responsive to detecting apresence of the occupant in the space; and selecting, by the controlcircuitry, a second target color temperature for the space responsive toan absence of the occupant in the space, the second target colortemperature different than the first target color temperature.
 11. Themethod of claim 10 wherein selecting the first target color temperaturefor the space responsive to detecting the presence of the occupant inthe space and selecting the second target color temperature for thespace responsive to the absence of the occupant in the space furthercomprises: selecting, by the control circuitry, a relatively warmerfirst target color temperature for the space responsive to detecting thepresence of the occupant in the space; and selecting, by the controlcircuitry, a relatively cooler second target color temperature for thespace responsive to the absence of the occupant in the space.
 12. Themethod of claim 1, further comprising: receiving, by the controlcircuitry, an input signal to decrease a first output intensity of thefirst lighting load and a second output intensity of the second lightingload; communicating to the first lighting load a third control outputsignal to reduce the first output level of the first lighting load; andcommunicating to the second lighting load a fourth control output signalto reduce the second output level of the second lighting load whilemaintaining the ratio of the first output level to the second outputlevel.
 13. The method of claim 2, further comprising: receiving, by thecontrol circuitry, an input signal to decrease a first output intensityof the first lighting load and a second output intensity of the secondlighting load; communicating to the first lighting load a third controloutput signal to reduce the first output level while maintaining thefirst color temperature of the first lighting load; and communicating tothe second lighting load a fourth control output signal to reduce thesecond output level of the second lighting load while varying the ratioof the first output level to the second output level to produce a warmercolor temperature as the first output level and the second output leveldecrease.
 14. A lighting color temperature control system, comprising:one or more sensors disposed in a space, the one or more sensors toprovide an output signal; a first lighting load to provide illuminationat a first color temperature; a second lighting load to provideillumination at a second color temperature, the second color temperaturedifferent from the first color temperature; control circuitrycommunicatively couplable to the one or more sensors, the first lightingload, and to the second lighting load, the control circuitry to: receivethe output signal from the one or more sensors; determine a target colortemperature for the space based on the received output signal; determinea ratio of a first output level of light having a first colortemperature to a second output level of light having a second colortemperature different from the first color temperature to achieve thetarget color temperature; communicate a first control output thatincludes data indicative of the determined first output level, the firstcontrol output to cause the first lighting load to provide illuminationat the first color temperature at the first output level; andcommunicate a second control output that includes data indicative of thedetermined second output level, the second control output to cause thesecond lighting load to provide illumination at the second colortemperature at the second output level.
 15. The system of claim 14,wherein the first lighting load and the second lighting load aredisposed in a single lighting fixture.
 16. The system of claim 15wherein the control circuitry is disposed remote from the first lightingload and the second lighting load.
 17. The system of claim 14 whereinthe first lighting load is disposed in a first lighting fixture and thesecond lighting load is disposed in a second lighting fixture, thesecond lighting fixture remote from the first lighting fixture.
 18. Thesystem of claim 17 wherein the control circuitry is disposed proximateeither the first lighting fixture or the second lighting fixture. 19.The system of claim 17 wherein at least a portion of the controlcircuitry is disposed in the first lighting fixture and at least aportion of the control circuitry is disposed in the second lightingfixture.
 20. The system of claim 14: wherein the one or more sensorsinclude one or more daylight sensors disposed in the space; and whereinthe output signal provided by the one or more daylight sensors includesinformation indicative of a measured color temperature of daylightpresent in the space.
 21. The system of claim 20, the control circuitryto further: determine the target color temperature using the measuredcolor temperature of the daylight present in the space.
 22. The systemof claim 14: wherein the one or more sensors include one or moreoccupancy sensors disposed in the space; and wherein the output signalprovided by the one or more occupancy sensors information indicative ofan occupant present in the space.
 23. The system of claim 22, thecontrol circuitry to further: select a first target color temperatureresponsive to detecting a presence of the occupant in the space; andselect a second target color temperature responsive to an absence of theoccupant in the space, the second target color temperature differentthan the first target color temperature.
 24. The system of claim 22, thecontrol circuitry to further: select a relatively warmer first targetcolor temperature for the space responsive to detecting the presence ofthe occupant in the space; and select a relatively cooler second targetcolor temperature for the space responsive to the absence of theoccupant in the space.
 25. The system of claim 14, the control circuitryto further: receive an input signal to decrease the first output levelof the first lighting load and the second output level of the secondlighting load; communicate to the first lighting load a third controloutput signal to reduce the first output level of the first lightingload; and communicate to the second lighting load a fourth controloutput signal to reduce the second output level of the second lightingload while maintaining the ratio of the first output level to the secondoutput level.
 26. The system of claim 14, the control circuitry tofurther: receive an input signal to decrease the first output level ofthe first lighting load and the second output level of the secondlighting load; communicate to the first lighting load a third controloutput signal to reduce the first output level of the first lightingload; and communicate to the second lighting load a fourth controloutput signal to reduce the second output level of the second lightingload while varying the ratio of the first output level to the secondoutput level to produce a warmer color temperature as the first outputlevel and the second output level decrease.
 27. A non-transitory,machine-readable, storage device that includes instructions that whenexecuted by control circuitry, cause the control circuitry to: determinea target color temperature for the space based on an output signalreceived from one or more communicatively coupled sensors; determine aratio of a first output level of light having a first color temperatureto a second output level of light having a second color temperaturedifferent from the first color temperature to achieve the target colortemperature; communicate, via communications interface circuitrycommunicatively coupled to the control circuitry, a first control outputthat includes data indicative of the determined first output level, thefirst control output to cause a first lighting load to provideillumination at the first color temperature at the first output level;communicate, via the communications interface circuitry, a secondcontrol output that includes data indicative of the determined secondoutput level, the second control output to cause a second lighting loadto provide illumination at the second color temperature at the secondoutput level.